Xi uses which web standards

As with the i element, authors can use the class attribute on the b element to identify why the element is being used, so that if the style of a particular use is to be changed at a later date, the author doesn't have to go through annotating each use.

The b element should be used as a last resort when no other element is more appropriate. In particular, headings should use the h1 to h6 elements, stress emphasis should use the em element, importance should be denoted with the strong element, and text marked or highlighted should use the mark element.

In the previous example, the correct element to use would have been strong , not b. Style sheets can be used to format b elements, just like any other element can be restyled. Thus, it is not the case that content in b elements will necessarily be boldened. HTML element represents a span of inline text which should be rendered in a way that indicates that it has a non-textual annotation.

This is rendered by default as a simple solid underline, but may be altered using CSS. The u element represents a span of text with an unarticulated, though explicitly rendered, non-textual annotation, such as labeling the text as being a proper name in Chinese text a Chinese proper name mark , or labeling the text as being misspelt.

In most cases, another element is likely to be more appropriate: for marking stress emphasis, the em element should be used; for marking key words or phrases either the b element or the mark element should be used, depending on the context; for marking book titles, the cite element should be used; for labeling text with explicit textual annotations, the ruby element should be used; for technical terms, taxonomic designation, transliteration, a thought, or for labeling ship names in Western texts, the i element should be used.

The default rendering of the u element in visual presentations clashes with the conventional rendering of hyperlinks underlining. Authors are encouraged to avoid using the u element where it could be confused for a hyperlink. In this example, a u element is used to mark a word as misspelt:. HTML element represents text which is marked or highlighted for reference or notation purposes, due to the marked passage's relevance or importance in the enclosing context. The mark element represents a run of text in one document marked or highlighted for reference purposes, due to its relevance in another context.

When used in a quotation or other block of text referred to from the prose, it indicates a highlight that was not originally present but which has been added to bring the reader's attention to a part of the text that might not have been considered important by the original author when the block was originally written, but which is now under previously unexpected scrutiny. When used in the main prose of a document, it indicates a part of the document that has been highlighted due to its likely relevance to the user's current activity.

This example shows how the mark element can be used to bring attention to a particular part of a quotation:. If the goal was to mark the element as misspelt, however, the u element, possibly with a class, would be more appropriate. Another example of the mark element is highlighting parts of a document that are matching some search string.

If someone looked at a document, and the server knew that the user was searching for the word "kitten", then the server might return the document with one paragraph modified as follows:.

This is separate from syntax highlighting , for which span is more appropriate. Combining both, one would get:. This is another example showing the use of mark to highlight a part of quoted text that was originally not emphasized. In this example, common typographic conventions have led the author to explicitly style mark elements in quotes to render in italics. Note, incidentally, the distinction between the em element in this example, which is part of the original text being quoted, and the mark element, which is highlighting a part for comment.

The following example shows the difference between denoting the importance of a span of text strong as opposed to denoting the relevance of a span of text mark. It is an extract from a textbook, where the extract has had the parts relevant to the exam highlighted. The safety warnings, important though they may be, are apparently not relevant to the exam. HTML element tells the browser's bidirectional algorithm to treat the text it contains in isolation from its surrounding text. It's particularly useful when a website dynamically inserts some text and doesn't know the directionality of the text being inserted.

Content attributes : Global attributes Also, the dir global attribute has special semantics on this element. The bdi element represents a span of text that is to be isolated from its surroundings for the purposes of bidirectional text formatting.

The dir global attribute defaults to auto on this element it never inherits from the parent element like with other elements. This element has rendering requirements involving the bidirectional algorithm. This element is especially useful when embedding user-generated content with an unknown directionality. In this example, usernames are shown along with the number of posts that the user has submitted.

If the bdi element were not used, the username of the Arabic user would end up confusing the text the bidirectional algorithm would put the colon and the number "3" next to the word "User" rather than next to the word "posts". HTML element overrides the current directionality of text, so that the text within is rendered in a different direction.

The bdo element represents explicit text directionality formatting control for its children. It allows authors to override the Unicode bidirectional algorithm by explicitly specifying a direction override. Authors must specify the dir attribute on this element, with the value ltr to specify a left-to-right override and with the value rtl to specify a right-to-left override. The auto value must not be specified. HTML element is a generic inline container for phrasing content, which does not inherently represent anything.

It can be used to group elements for styling purposes using the class or id attributes , or because they share attribute values, such as lang. It should be used only when no other semantic element is appropriate. In this example, a code fragment is marked up using span elements and class attributes so that its keywords and identifiers can be color-coded from CSS:. HTML element produces a line break in text carriage-return. It is useful for writing a poem or an address, where the division of lines is significant.

Content model : Nothing. While line breaks are usually represented in visual media by physically moving subsequent text to a new line, a style sheet or user agent would be equally justified in causing line breaks to be rendered in a different manner, for instance as green dots, or as extra spacing. The following example is correct usage of the br element:. The following examples are non-conforming, as they abuse the br element:.

If a paragraph consists of nothing but a single br element, it represents a placeholder blank line e. Such blank lines must not be used for presentation purposes. Any content inside br elements must not be considered part of the surrounding text. HTML element represents a word break opportunity—a position within text where the browser may optionally break a line, though its line-breaking rules would not otherwise create a break at that location. Categories : Flow content.

The wbr element represents a line break opportunity. In the following example, someone is quoted as saying something which, for effect, is written as one long word.

However, to ensure that the text can be wrapped in a readable fashion, the individual words in the quote are separated using a wbr element. Any content inside wbr elements must not be considered part of the surrounding text. Links are a conceptual construct, created by a , area , form , and link elements, that represent a connection between two resources, one of which is the current Document. There are two kinds of links in HTML:. These are links to resources that are to be used to augment the current document, generally automatically processed by the user agent.

All external resource links have a fetch and process the linked resource algorithm which describes how the resource is obtained. Hyperlinks These are links to other resources that are generally exposed to the user by the user agent so that the user can cause the user agent to navigate to those resources, e. For link elements with an href attribute and a rel attribute, links must be created for the keywords of the rel attribute, as defined for those keywords in the link types section.

Similarly, for a and area elements with an href attribute and a rel attribute, links must be created for the keywords of the rel attribute as defined for those keywords in the link types section.

Unlike link elements, however, a and area elements with an href attribute that either do not have a rel attribute, or whose rel attribute has no keywords that are defined as specifying hyperlinks , must also create a hyperlink. This implied hyperlink has no special meaning it has no link type beyond linking the element's node document to the resource given by the element's href attribute.

Similarly, for form elements with a rel attribute, links must be created for the keywords of the rel attribute as defined for those keywords in the link types section. A hyperlink can have one or more hyperlink annotations that modify the processing semantics of that hyperlink.

The href attribute on a and area elements must have a value that is a valid URL potentially surrounded by spaces. The href attribute on a and area elements is not required; when those elements do not have href attributes they do not create hyperlinks. The target attribute, if present, must be a valid browsing context name or keyword. It gives the name of the browsing context that will be used. User agents use this name when following hyperlinks.

When an a or area element's activation behavior is invoked, the user agent may allow the user to indicate a preference regarding whether the hyperlink is to be used for navigation or whether the resource it specifies is to be downloaded. In the absence of a user preference, the default should be navigation if the element has no download attribute, and should be to download the specified resource if it does. Whether determined by the user's preferences or via the presence or absence of the attribute, if the decision is to use the hyperlink for navigation then the user agent must follow the hyperlink , and if the decision is to use the hyperlink to download a resource, the user agent must download the hyperlink.

These terms are defined in subsequent sections below. The download attribute, if present, indicates that the author intends the hyperlink to be used for downloading a resource. The attribute may have a value; the value, if any, specifies the default filename that the author recommends for use in labeling the resource in a local file system.

There are no restrictions on allowed values, but authors are cautioned that most file systems have limitations with regard to what punctuation is supported in filenames, and user agents are likely to adjust filenames accordingly. The value is used by the user agent for hyperlink auditing. The rel attribute on a and area elements controls what kinds of links the elements create.

The attribute's value must be an unordered set of unique space-separated tokens. The allowed keywords and their meanings are defined below. The possible supported tokens are noreferrer , noopener , and opener. The rel attribute has no default value.

If the attribute is omitted or if none of the values in the attribute are recognized by the user agent, then the document has no particular relationship with the destination resource other than there being a hyperlink between the two. The hreflang attribute on a elements that create hyperlinks , if present, gives the language of the linked resource.

It is purely advisory. The value must be a valid BCP 47 language tag. The type attribute, if present, gives the MIME type of the linked resource. The value must be a valid MIME type string. User agents must not consider the type attribute authoritative — upon fetching the resource, user agents must not use metadata included in the link to the resource to determine its type.

The referrerpolicy attribute is a referrer policy attribute. Its purpose is to set the referrer policy used when following hyperlinks. It is initially null. If this element's href content attribute is absent, set this element's url to null.

Otherwise, parse this element's href content attribute value relative to this element's node document. If parsing is successful, set this element's url to the result; otherwise, set this element's url to null. When elements implementing the HTMLHyperlinkElementUtils mixin are created, and whenever those elements have their href content attribute set, changed, or removed, the user agent must set the url.

If element's url is non-null, its scheme is " blob ", and it has an opaque path , then terminate these steps. Set the url. To update href , set the element's href content attribute's value to the element's url , serialized. The href getter steps are:. Reinitialize url. Let url be this 's url. If url is null and this has no href content attribute, return the empty string. Otherwise, if url is null, return this 's href content attribute's value.

Return url , serialized. The href setter steps are to set this 's href content attribute's value to the given value. The origin getter steps are:. If this 's url is null, return the empty string. Return the serialization of this 's url 's origin. The protocol getter steps are:. If this 's url is null, return " : ". Return this 's url 's scheme , followed by " : ".

The protocol setter steps are:. If this 's url is null, then return. Basic URL parse the given value, followed by " : ", with this 's url as url and scheme start state as state override. Because the URL parser ignores multiple consecutive colons, providing a value of " https: " or even " https " is the same as providing a value of " https ". Update href. The username getter steps are:. Return this 's url 's username.

The username setter steps are:. Set the username , given url and the given value. The password getter steps are:.

If url is null, then return the empty string. Return url 's password. The password setter steps are:. Set the password , given url and the given value. The host getter steps are:. If url or url 's host is null, return the empty string. If url 's port is null, return url 's host , serialized.

Return url 's host , serialized , followed by " : " and url 's port , serialized. The host setter steps are:. If url is null or url has an opaque path , then return. Basic URL parse the given value, with url as url and host state as state override. The hostname getter steps are:. Return url 's host , serialized. The hostname setter steps are:. Basic URL parse the given value, with url as url and hostname state as state override.

The port getter steps are:. If url or url 's port is null, return the empty string. Return url 's port , serialized. The port setter steps are:.

If the given value is the empty string, then set url 's port to null. Otherwise, basic URL parse the given value, with url as url and port state as state override. The pathname getter steps are:. Return the result of URL path serializing url. The pathname setter steps are:. Set url 's path to the empty list.

Basic URL parse the given value, with url as url and path start state as state override. The search getter steps are:. If url is null, or url 's query is either null or the empty string, return the empty string. Return "? The search setter steps are:. If url is null, terminate these steps. If the given value is the empty string, set url 's query to null. Let input be the given value with a single leading "? Set url 's query to the empty string.

Basic URL parse input , with null, this element's node document 's document's character encoding , url as url , and query state as state override. The hash getter steps are:. If url is null, or url 's fragment is either null or the empty string, return the empty string. Return " ", followed by url 's fragment. The hash setter steps are:. If url is null, then return. If the given value is the empty string, set url 's fragment to null.

Let input be the given value with a single leading " " removed, if any. Set url 's fragment to the empty string. Basic URL parse input , with url as url and fragment state as state override.

This is also used by form submission for the form element. The exception for a elements is for compatibility with web content. To get an element's noopener , given an a , area , or form element element and a string target :.

If element 's link types include the noopener or noreferrer keyword, then return true. Return false. To follow the hyperlink created by an element subject , given an optional hyperlinkSuffix default null :.

If subject cannot navigate , then return. Let replace be false. Let source be subject 's node document 's browsing context. Let targetAttributeValue be the empty string. If subject is an a or area element, then set targetAttributeValue to the result of getting an element's target given subject.

Let noopener be the result of getting an element's noopener with subject and targetAttributeValue. Let target and windowType be the result of applying the rules for choosing a browsing context given targetAttributeValue , source , and noopener.

If target is null, then return. Parse a URL given subject 's href attribute, relative to subject 's node document. Otherwise, if parsing the URL failed, the user agent may report the error to the user in a user-agent-specific manner, may queue an element task on the DOM manipulation task source given subject to navigate the target browsing context to an error page to report the error, or may ignore the error and do nothing.

In any case, the user agent must then return. If hyperlinkSuffix is non-null, then append it to URL. Let request be a new request whose URL is URL and whose referrer policy is the current state of subject 's referrerpolicy content attribute. If subject 's link types includes the noreferrer keyword, then set request 's referrer to " no-referrer ". Let historyHandling be " replace " if windowType is not " existing or none "; otherwise, " default ".

Unlike many other types of navigations, following hyperlinks does not have special " replace " behavior for when documents are not completely loaded. This is true for both user-initiated instances of following hyperlinks, as well as script-triggered ones via, e. Queue an element task on the DOM manipulation task source given subject to navigate target to request with historyHandling set to historyHandling and the source browsing context set to source.

To indicate that a resource is intended to be downloaded for use later, rather than immediately used, the download attribute can be specified on the a or area element that creates the hyperlink to that resource. The attribute can furthermore be given a value, to specify the filename that user agents are to use when storing the resource in a file system. This is to protect users from being made to download sensitive personal or confidential information without their full understanding.

The following allowed to download algorithm takes an initiator browsing context and an instantiator browsing context , and returns a boolean indicating whether or not downloading is allowed:.

If the initiator browsing context 's sandboxing flags has the sandboxed downloads browsing context flag set, then return false. If the instantiator browsing context is non-null, and its sandboxing flags has the sandboxed downloads browsing context flag set, then return false. Optionally, the user agent may return false, if it believes doing so would safeguard the user from a potentially hostile download.

Return true. To download the hyperlink created by an element subject , given an optional hyperlinkSuffix default null :. Run the allowed to download algorithm with the subject 's node document 's browsing context and null. If the algorithm returns false, then return.

If parsing the URL fails, the user agent may report the error to the user in a user-agent-specific manner, may navigate to an error page to report the error, or may ignore the error and do nothing.

In either case, the user agent must return. Run these steps in parallel :. Let request be a new request whose URL is URL , client is entry settings object , initiator is " download ", destination is the empty string, and whose synchronous flag and use-URL-credentials flag are set. Handle the result of fetching request as a download. When a user agent is to handle a resource obtained from a fetch as a download , it should provide the user with a way to save the resource for later use, if a resource is successfully obtained.

Otherwise, it should report any problems downloading the file to the user. If the user agent needs a filename for a resource being handled as a download , it should select one using the following algorithm.

This algorithm is intended to mitigate security dangers involved in downloading files from untrusted sites, and user agents are strongly urged to follow it. Let filename be the undefined value. Let resource origin be the origin of the URL of the resource being downloaded, unless that URL's scheme component is data , in which case let resource origin be the same as the interface origin , if any.

If there is no interface origin , then let trusted operation be true. Otherwise, let trusted operation be true if resource origin is the same origin as interface origin , and false otherwise. Let proposed filename have the value of the download attribute of the element of the hyperlink that initiated the download at the time the download was initiated.

If trusted operation is true, let filename have the value of proposed filename , and jump to the step labeled sanitize below. Let filename be set to the user's preferred filename or to a filename selected by the user agent, and jump to the step labeled sanitize below.

If the algorithm reaches this step, then a download was begun from a different origin than the resource being downloaded, and the origin did not mark the file as suitable for downloading, and the download was not initiated by the user. This could be because a download attribute was used to trigger the download, or because the resource in question is not of a type that the user agent supports.

This could be dangerous, because, for instance, a hostile server could be trying to get a user to unknowingly download private information and then re-upload it to the hostile server, by tricking the user into thinking the data is from the hostile server.

Thus, it is in the user's interests that the user be somehow notified that the resource in question comes from quite a different source, and to prevent confusion, any suggested filename from the potentially hostile interface origin should be ignored. Sanitize : Optionally, allow the user to influence filename. For example, a user agent could prompt the user for a filename, potentially providing the value of filename as determined above as a default value.

Adjust filename to be suitable for the local file system. For example, this could involve removing characters that are not legal in filenames, or trimming leading and trailing whitespace. If the platform conventions do not in any way use extensions to determine the types of file on the file system, then return filename as the filename.

Let claimed type be the type given by the resource's Content-Type metadata , if any is known. Let named type be the type given by filename 's extension , if any is known. For the purposes of this step, a type is a mapping of a MIME type to an extension. If named type is consistent with the user's preferences e. If claimed type and named type are the same type i. If the claimed type is known, then alter filename to add an extension corresponding to claimed type.

Otherwise, if named type is known to be potentially dangerous e. This last step would make it impossible to download executables, which might not be desirable. As always, implementers are forced to balance security and usability in this matter. Return filename as the filename. For the purposes of this algorithm, a file extension consists of any part of the filename that platform conventions dictate will be used for identifying the type of the file.

For example, many operating systems use the part of the filename following the last dot ". User agents should ignore any directory or path information provided by the resource itself, its URL , and any download attribute, in deciding where to store the resulting file in the user's file system. If a hyperlink created by an a or area element has a ping attribute, and the user follows the hyperlink, and the value of the element's href attribute can be parsed , relative to the element's node document , without failure, then the user agent must take the ping attribute's value, split that string on ASCII whitespace , parse each resulting token relative to the element's node document , and then run these steps for each resulting URL record ping URL , ignoring tokens that fail to parse:.

Optionally, return. For example, the user agent might wish to ignore any or all ping URLs in accordance with the user's expressed preferences. Fetch request. This may be done in parallel with the primary fetch, and is independent of the result of that fetch. Based on the user's preferences, UAs may either ignore the ping attribute altogether, or selectively ignore URLs in the list e. User agents must ignore any entity bodies returned in the responses. User agents may close the connection prematurely once they start receiving a response body.

When the ping attribute is present, user agents should clearly indicate to the user that following the hyperlink will also cause secondary requests to be sent in the background, possibly including listing the actual target URLs.

For example, a visual user agent could include the hostnames of the target ping URLs along with the hyperlink's actual URL in a status bar or tooltip. The ping attribute is redundant with pre-existing technologies like HTTP redirects and JavaScript in allowing web pages to track which off-site links are most popular or allowing advertisers to track click-through rates. However, the ping attribute provides these advantages to the user over those alternatives:.

Thus, while it is possible to track users without this feature, authors are encouraged to use the ping attribute so that the user agent can make the user experience more transparent. This table is non-normative; the actual definitions for the link types are given in the next few sections.

In this section, the term referenced document refers to the resource identified by the element representing the link, and the term current document refers to the resource within which the element representing the link finds itself.

To determine which link types apply to a link , a , area , or form element, the element's rel attribute must be split on ASCII whitespace. The resulting tokens are the keywords for the link types that apply to that element. Except where otherwise specified, a keyword must not be specified more than once per rel attribute. Some of the sections that follow the table below list synonyms for certain keywords. The indicated synonyms are to be handled as specified by user agents, but must not be used in documents for example, the keyword " copyright ".

Keywords that are body-ok affect whether link elements are allowed in the body. The body-ok keywords are dns-prefetch , modulepreload , pingback , preconnect , prefetch , preload , prerender , and stylesheet. New link types that are to be implemented by web browsers are to be added to this standard.

The remainder can be registered as extensions. Chrome Android? WebView Android? Samsung Internet? Opera Android?

The alternate keyword may be used with link , a , and area elements. The alternate keyword modifies the meaning of the stylesheet keyword in the way described for that keyword. The alternate keyword does not create a link of its own. Here, a set of link elements provide some style sheets:. The keyword creates a hyperlink referencing a syndication feed though not necessarily syndicating exactly the same content as the current page.

If the user agent has the concept of a default syndication feed, the first such element in tree order should be used as the default. The following link elements give syndication feeds for a blog:. Such link elements would be used by user agents engaged in feed autodiscovery, with the first being the default where applicable.

The following example offers various different syndication feeds to the user, using a elements:. The keyword creates a hyperlink referencing an alternate representation of the current document.

The nature of the referenced document is given by the hreflang , and type attributes. If the alternate keyword is used with the hreflang attribute, and that attribute's value differs from the document element 's language , it indicates that the referenced document is a translation. If the alternate keyword is used with the type attribute, it indicates that the referenced document is a reformulation of the current document in the specified format.

The hreflang and type attributes can be combined when specified with the alternate keyword. The following example shows how you can specify versions of the page that use alternative formats, are aimed at other languages, and that are intended for other media:. This relationship is transitive — that is, if a document links to two other documents with the link type " alternate ", then, in addition to implying that those documents are alternative representations of the first document, it is also implying that those two documents are alternative representations of each other.

The author keyword may be used with link , a , and area elements. This keyword creates a hyperlink. For a and area elements, the author keyword indicates that the referenced document provides further information about the author of the nearest article element ancestor of the element defining the hyperlink, if there is one, or of the page as a whole, otherwise.

For link elements, the author keyword indicates that the referenced document provides further information about the author for the page as a whole. The "referenced document" can be, and often is, a mailto: URL giving the email address of the author. Synonyms : For historical reasons, user agents must also treat link , a , and area elements that have a rev attribute with the value " made " as having the author keyword specified as a link relationship.

The bookmark keyword may be used with a and area elements. The bookmark keyword gives a permalink for the nearest ancestor article element of the linking element in question, or of the section the linking element is most closely associated with , if there are no ancestor article elements. The following snippet has three permalinks. A user agent could determine which permalink applies to which part of the spec by looking at where the permalinks are given.

The canonical keyword may be used with link element. That helps search engines reduce duplicate content, as described in more detail in The Canonical Link Relation. The dns-prefetch keyword may be used with link elements. This keyword creates an external resource link. This keyword is body-ok. The dns-prefetch keyword indicates that preemptively performing DNS resolution for the origin of the specified resource is likely to be beneficial, as it is highly likely that the user will require resources located at that origin , and the user experience would be improved by preempting the latency costs associated with DNS resolution.

User agents must implement the processing model of the dns-prefetch keyword described in Resource Hints. There is no default type for resources given by the dns-prefetch keyword. The codes for subdivisions are represented as the alpha-2 code for the country, followed by up to three characters. Names and codes for subdivisions are usually taken from relevant official national information sources.

The formerly used codes are four-letter codes alpha How the alpha-4 codes are constructed depends on the reason why the country name has been removed. Read more about the different types of codes in the Glossary for ISO For more information, visit the ISO Store. ISO is regularly updated to reflect changes in country names and subdivisions. The numeric country code is assigned by the UN. As a general rule, the ISO Maintenance Agency does not assign official country code elements to other geopolitical areas or countries that are not member states of the UN.

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