The target, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present.

Represents an abbreviation or acronym. The optional title attribute may be used to provide an expansion of the abbreviation. If specified, the title attribute must contain an expansion of the abbreviation and nothing else.

Represents the contact information for its enclosing section. If it is a child of the body element, then it applies to the document as a whole.

If the area element has no href attribute, then the area represented by the element cannot be selected, and the alt attribute must be omitted.

Represents a section of a page that consists of a composition that forms an independent part of a document, page, or site. This could be a forum post, a magazine or newspaper article, a Web log entry, a user-submitted comment, or any other independent item of content.

Represents a section of a page consisting of content that is tangentially related to the content around the aside element, and which could be considered separate from that content. Such sections are often represented as sidebars in printed typography.

Chrome 3+ supports .ogg and .wav Firefox 3.5+ supports .ogg and .wav Opera 10.5+ supports .ogg and .wav Safari 4+ supports .mp3 and .wav

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.

There must be no more than one base element per document. A base element must have either an href attribute, a target attribute, or both.

The bdi element represents a span of text that is to be isolated from its surroundings for the purposes of bidirectional text formatting.

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.

Content inside a blockquote must be quoted from another source, whose address, if it has one, may be cited in the cite attribute.

The body element represents the main content of the document.

The br element represents a line break. br elements must be used only for line breaks that are actually part of the content, as in poems or addresses. br elements must not be used for separating thematic groups in a paragraph.

The button element represents a button. If the element is not disabled, then the user agent should allow the user to activate the button.

When authors use the canvas element, they must also provide content that, when presented to the user, conveys essentially the same function or purpose as the bitmap canvas. This content should be nested within the canvas element as a fallback.

When a table element is the only content in a figure element other than the figcaption, the caption element should be omitted in favor of the figcaption.

A person's name is not the title of a work — even if people call that person a piece of work — and the element must therefore not be used to mark up people's names. (In some cases, the b element might be appropriate for names e.g. in a gossip article where the names of famous people are keywords rendered with a different style to draw attention to them. In other cases, if an element is really needed, the span element can be used.)

The code element represents a fragment of computer code. This could be an XML element name, a filename, a computer program, or any other string that a computer would recognize.

If a col element has a parent and that is a colgroup element that itself has a parent that is a table element, then the col element represents one or more columns in the column group represented by that colgroup.

If the colgroup element contains no col elements, then the element may have a span content attribute specified, whose value must be a valid non-negative integer greater than zero.

The datalist element is hooked up to an input element using the list attribute on the input element.

The dd element represents the description, definition, or value, part of a term-description group in a description list (dl element).

The del element represents a removal from the document. Thedel elements should not cross implied paragraph boundaries

The details element represents a disclosure widget from which the user can obtain additional information or controls. However, the details element is not appropriate for footnotes.

The dfn element represents the defining instance of a term. The paragraph, description list group, or section that is the nearest ancestor of the dfn element must also contain the definition(s) for the term given by the dfn element.

The div element has no special meaning at all. It represents its children. It can be used with the class, lang, and title attributes to mark up semantics common to a group of consecutive elements.

Name-value groups may be terms and definitions, metadata topics and values, or any other groups of name-value data. The values within a group are alternatives multiple paragraphs forming part of the same value must all be given within the same dd element.

A string that is an ASCII case-insensitive match for the string ").

The dt element represents the term, or name, part of a term-description group in a description list (dl element).

Represents stress emphasis of its contents. The level of emphasis that a particular piece of content has is given by its number of ancestor em elements. The 'stress' being referred to is linguistic. If spoken, this stress would be emphasised pronunciation on a word that can change the nuance of a sentence.

The optional type attribute specifies the MIME type of the plugin to instantiate. The value must be a valid MIME type, optionally with parameters. If both the type attribute and the src attribute are present, then the type attribute must specify the same MIME type as the explicit Content-Type metadata of the resource given by the src attribute.

The child is a legend element. The child is not out-of-flow (e.g. not absolutely positioned or floated). The child is generating a box (e.g. it is not 'display:none').

The figcaption element represents a caption or legend for the rest of the contents of the figcaption element's parent figure element, if any.

The figure element can be used to annotate illustrations, diagrams, photos, code listings, etc., that are referenced in the main content of the document, but that could, without affecting the flow of the document, be moved away from that primary content — e.g., to the side of the page, to dedicated pages, or to an appendix.

Represents the "footer" of a document or section of a document. The footer element typically contains metadata about its enclosing section, such as who wrote it, links to related documents, copyright data, etc. Contact information for the section given in a footer should be marked up using the address element.

The form element represents a collection of form-associated elements, some of which can represent editable values that can be submitted to a server for processing.

The head element represents a collection of metadata for the Document.

Represents the "header" of a document or section of a document. The header element is typically used to group a set of h1–h6 elements to mark up a page's title with its subtitle or tagline. header elements may, however, contain more than just the section's headings and subheadings — e.g., version history information or publication date.

Represent headings and subheadings. These elements rank in importance according to the number in their name. The h1 element is said to have the highest rank, the h6 element has the lowest rank, and two elements with the same name have equal rank.

Represents a paragraph-level thematic break. The "paragraph-level" bit means between blocks of text, so it can't be used to separate sections of a site. Instead, hr now separates different topics within a section of prose, or between scenes in a novel.

The html element represents the root of an HTML document.

Only use i when nothing more suitable is available — e.g., em for text with stress emphasis, strong for text with semantic importance, cite for titles in a citation or bibliography, dfn for defining a word, and var for mathematical variables.

Any number of comments and space characters. Optionally, a DOCTYPE. Any number of comments and space characters. The root element, in the form of an html element. Any number of comments and space characters.

The img element must not be used as a layout tool. In particular, img elements should not be used to display transparent images, as they rarely convey meaning and rarely add anything useful to the document.

The input element represents a typed data field, usually with a form control to allow the user to edit the data.

The ins element represents an addition to the document. The ins elements should not cross implied paragraph boundaries.

When the kbd element is nested inside another kbd element, it represents an actual key or other single unit of input as appropriate for the input mechanism.

The keygen element represents a key pair generator control. When the control's form is submitted, the private key is stored in the local keystore, and the public key is packaged and sent to the server.

The label represents a caption in a user interface. The caption can be associated with a specific form control, known as the label element's labeled control, either using for attribute, or by putting the form control inside the label element itself.

The legend element represents a caption for the rest of the contents of the legend element's parent fieldset element, if any.

The li element represents a list item. If its parent element is an ol, ul, or menu element, then the element is an item of the parent element's list, as defined for those elements. Otherwise, the list item has no defined list-related relationship to any other li element.

A link element must have rel attribute.

The main element is an exact analogue of ARIA's role="main", and is designed to show screenreaders and assistive technologies exactly where main content begins, so it can be a target for a "skip links" keyboard command, for example. It could also be used for content syndication (Instapaper-ish things) mobile browsers could zoom in on main when encountering non-responsive websites.It should therefore be used once per page. If you use something like(or similar, such as ), simply replace that with .

The map element, in conjunction with any area element descendants, defines an image map. The element represents its children.

When used in a quotation or other block of text referenced in a document, it indicates a highlight that was not present in the original document — e.g., a portion of text in an academic publication that has recently come under additional scrutiny.

If a menu element's type attribute is in the list state, then the element either represents an unordered list of items (each represented by an li element), each of which represents a command that the user can perform or activate, or, if the element has no li element children, flow content describing available commands.

The meta element can represent document-level metadata with the name attribute, pragma directives with the http-equiv attribute, and the file's character encoding declaration when an HTML document is serialized to string form (e.g. for transmission over the network or for disk storage) with the charset attribute.

When the element is wider than it is tall(or square), the depiction is expected to be of a horizontal gauge, with the minimum value on the right if the 'direction' property on this element has a computed value of 'rtl', and on the left otherwise. When the element is taller than it is wide, it is expected to depict a vertical gauge, with the minimum value on the bottom.

Not all groups of links on a page need to be in a nav element — only groups of primary navigation links. In particular, it is common for footers to have a list of links to various key parts of a site, but the footer element is more appropriate in such cases.

The noscript element represents nothing if scripting is enabled, and represents its children if scripting is disabled. It is used to present different markup to user agents that support scripting and those that don't support scripting, by affecting how the document is parsed.

The object element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin.

The ol element represents a list of items, where the items have been intentionally ordered, such that changing the order would change the meaning of the list.

When showing option elements in select elements, user agents should show the option elements of such groups as being related to each other and separate from other option elements.

In certain circumstances described in the definition of the select element, an option element can be a select element's placeholder label option. A placeholder label option does not represent an actual option, but instead represents a label for the select control.

The p element represents a paragraph.

The param element defines parameters for plugins invoked by object elements. It does not represent anything on its own.

The pre element represents a block of preformatted text, in which structure is represented by typographic conventions rather than by elements.

Represents the completion progress of a task. Progress may be either indeterminate — meaning it is unclear how much work remains before the task is complete (e.g., the task is waiting for a response from a remote host) — or a numeric value between 0 and a given maximum, explicitly specifying the fraction of work that has so far been completed.

The q element represents some phrasing content quoted from another source.

Represents a container for parentheses used to wrap ruby text () inside aelement. These are displayed by browsers which don't support , allowing for graceful degradation of ruby content. Browsers which supporthidevia display:none.

Represents a container for ruby text inside aelement.content becomes the small annotations rendered by default above horizontal base text or to the right of vertical base text.

Represents a container for base text and ruby text — small annotations used for phonetic readings in languages such as Japanese and Chinese. Examples include furigana and zhùyin fúhào (bopomofo).

The s element represents contents that are no longer accurate or no longer relevant.

The samp element represents (sample) output from a program or computing system

The script element allows authors to include dynamic script and data blocks in their documents. The element does not represent content for the user.

Represents a generic document or application section. In this context, a section is a thematic grouping of content, typically with a header, possibly with a footer. Examples include chapters in a book, the various tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A web site's home page could be split into sections for an introduction, news items, contact information.

The select element represents a control for selecting amongst a set of options.

Represents side comments such as small print. It is not intended to be presentational. The small element should not be used for extended spans of text such as multiple paragraphs, lists, or sections of text. It is only intended for short runs of text.

The source element allows authors to specify multiple alternative media resources for media elements. It does not represent anything on its own. The src attribute gives the address of the media resource. The value must be a valid non-empty URL potentially surrounded by spaces. This attribute must be present.

The span element doesn't mean anything on its own, but can be useful when used together with the global attributes, e.g. class, lang, or dir. It represents its children.

Represents strong importance for its contents. Indicate relative importance by nesting strong elements each strong element increases the importance of its contents. Changing the importance of a piece of text with the strong element does not change the meaning of the sentence.

The style element allows authors to embed style information in their documents. The style element is one of several inputs to the styling processing model. The element does not represent content for the user.

The sub element can be used inside a var element, for variables that have subscripts.

The summary element represents a summary, caption, or legend for the rest of the contents of the summary element's parent details element, if any.

The sup element represents a superscript and the sub element represents a subscript.

The table element represents data with more than one dimension, in the form of a table. Tables must not be used as layout aids.

The tbody element represents a block of rows that consist of a body of data for the parent table element, if the tbody element has a parent and it is a table.

The td element represents a data cell in a table.

The tfoot element represents the block of rows that consist of the column summaries (footers) for the parent table element, if the tfoot element has a parent and it is a table.

The th element represents a header cell in a table.

The thead element represents the block of rows that consist of the column labels (headers) for the parent table element, if the thead element has a parent and it is a table.

Represents a precise date and/or time in the proleptic Gregorian calendar. The time element encodes modern dates and times in a machine-readable way, so that, for example, user agents could offer to add an event to the user's calendar.

The title element represents the document's title or name. Authors should use titles that identify their documents even when they are used out of context, for example in a user's history or bookmarks, or in search results. The document's title is often different from its first heading, since the first heading does not have to stand alone when taken out of context.

The tr element represents a row of cells in a table.

The track element allows authors to specify explicit external timed text tracks for media elements. It does not represent anything on its own.

The u element represents a span of text with an unarticulated, though explicitly rendered, non-textual annotation (when you are annotating something, but not explicitly saying what it is). Examples include indicating misspelt words, labeling proper names in traditional Chinese prose, or indicating a family name when the name’s order is non-western.

The ul element represents a list of items, where the order of the items is not important — that is, where changing the order would not materially change the meaning of the list.

The var element represents a variable. This could be an actual variable in a mathematical expression or programming context, or it could just be a term used as a placeholder in prose.

Content may be nested inside the element. User agents should not show this content to the user. Authors should use this content to force older browsers to use a legacy plugin or to inform the user of how to access the content.

The wbr element represents a line break opportunity. Any content inside wbr elements must not be considered part of the surrounding text.