MiscellaneousAttributes

Specifies the horizontal alignment of the element. Mostly obsolete since HTML5

MDN

This attribute defines the alternative text describing the image. Users will see this displayed if the image URL is wrong, the image is not in one of the supported formats, or until the image is downloaded.

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Declares the character encoding of the page or script. Used on meta and script elements.

MDN

This attribute gives the value associated with the http-equiv or name attribute, depending of the context.

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A set of values specifying the coordinates of the hot-spot region. The number and meaning of the values depend upon the value specified for the shape attribute. For a rect or rectangle shape, the coords value is two x,y pairs: left, top, right, and bottom. For a circle shape, the value is x,y,r where x,y is a pair specifying the center of the circle and r is a value for the radius. For a poly or polygon shape, the value is a set of x,y pairs for each point in the polygon: x1,y1,x2,y2,x3,y3, and so on. In HTML4, the values are numbers of pixels or percentages, if a percent sign (%) is appended; in HTML5, the values are numbers of CSS pixels.

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This attribute indicates the time and date of the element and must be a valid date with an optional time string. If the value cannot be parsed as a date with an optional time string, the element does not have an associated time stamp.

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This Boolean attribute indicates that the form control is not available for interaction. In particular, the click event will not be dispatched on disabled controls. Also, a disabled control's value isn't submitted with the form.

This attribute is ignored if the value of the type attribute is hidden.

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This attribute instructs browsers to download a URL instead of navigating to it, so the user will be prompted to save it as a local file. If the attribute has a value, it is used as the pre-filled file name in the Save prompt (the user can still change the file name if they want). There are no restrictions on allowed values, though / and \ are converted to underscores. Most file systems limit some punctuation in file names, and browsers will adjust the suggested name accordingly.

MDN HTML5

For use in <meter> tags.

This is the single required attribute for anchors defining a hypertext source link. It indicates the link target, either a URL or a URL fragment. A URL fragment is a name preceded by a hash mark (#), which specifies an internal target location (an ID) within the current document. URLs are not restricted to Web (HTTP)-based documents. URLs might use any protocol supported by the browser. For example, file, ftp, and mailto work in most user agents.

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This enumerated attribute defines the pragma that can alter servers and user-agents behavior. The value of the pragma is defined using the content attribute and can be one of the following:

content-language content-type default-style refresh set-cookie

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Image URL, used to provide a picture to represent the command represented by a <menuitem>.

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Contains inline metadata, a base64-encoded cryptographic hash of a resource (file) you’re telling the browser to fetch, that a user agent can use to verify that a fetched resource has been delivered free of unexpected manipulation.

This Boolean attribute indicates that the image is part of a server-side map. If so, the precise coordinates of a click are sent to the server.

Note: This attribute is allowed only if the <img> element is a descendant of an <a> element with a valid href attribute.

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For use in <meter> tags.

This attribute specifies the media which the linked resource applies to. Its value must be a media query. This attribute is mainly useful when linking to external stylesheets by allowing the user agent to pick the best adapted one for the device it runs on.

This Boolean attribute indicates whether the details will be shown to the user on page load. Default is false and so details will be hidden.

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For use in <meter> tags.

This attribute specifies the name of a group of commands to be toggled as radio buttons when selected. May only be used where the type attribute is radio.

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This attribute names a relationship of the linked document to the current document. The attribute must be a space-separated list of the link types values. The most common use of this attribute is to specify a link to an external style sheet: the rel attribute is set to stylesheet, and the href attribute is set to the URL of an external style sheet to format the page.

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This Boolean attribute specifies that the items of the list are specified in reversed order.

MDN HTML5

The attribute describes the role(s) the current element plays in the context of the document. This can be used, for example, by applications and assistive technologies to determine the purpose of an element. This could allow a user to make informed decisions on which actions may be taken on an element and activate the selected action in a device independent way. It could also be used as a mechanism for annotating portions of a document in a domain specific way (e.g., a legal term taxonomy). Although the role attribute may be used to add semantics to an element, authors should use elements with inherent semantics, such as p, rather than layering semantics on semantically neutral elements, such as div role="paragraph".

See: http://www.w3.org/TR/role-attribute/#s_role_module_attributes

For use in <style> tags.

If this attribute is present, then the style applies only to its parent element. If absent, the style applies to the whole document.

This attribute was used to define a region for hyperlinks to create an image map. The values are circle, default, polygon, and rect. The format of the coords attribute depends on the value of shape. For circle, the value is x,y,r where x and y are the pixel coordinates for the center of the circle and r is the radius value in pixels. For rect, the coords attribute should be x,y,w,h. The x,y values define the upper-left-hand corner of the rectangle, while w and h define the width and height respectively. A value of polygon for shape requires x1,y1,x2,y2,... values for coords. Each of the x,y pairs defines a point in the polygon, with successive points being joined by straight lines and the last point joined to the first. The value default for shape requires that the entire enclosed area, typically an image, be used.

MDN HTML4 ONLY

This attribute defines the sizes of the icons for visual media contained in the resource. It must be present only if the rel contains the icon link types value. It may have the following values:

any, meaning that the icon can be scaled to any size as it is in a vectorial format, like image/svg+xml.

a white-space separated list of sizes, each in the format <width in pixels>x<height in pixels> or <width in pixels>X<height in pixels>. Each of these sizes must be contained in the resource.

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If the value of the type attribute is image, this attribute specifies a URI for the location of an image to display on the graphical submit button; otherwise it is ignored.

MDN

A list of one or more strings separated by commas indicating a set of possible image sources for the user agent to use. Each string is composed of:

1. a URL to an image

2. optionally, whitespace followed by one of:

a width descriptor, or a positive integer directly followed by 'w'. The width descriptor is divided by the source size given in the sizes attribute to calculate the effective pixel density.

a pixel density descriptor, which is a positive floating point number directly followed by 'x'.

If no descriptor is specified, the source is assigned the default descriptor: 1x.

It is incorrect to mix width descriptors and pixel density descriptors in the same srcset attribute. Duplicate descriptors (for instance, two sources in the same srcset which are both described with '2x') are invalid, too.

The user agent selects any one of the available sources at its discretion. This provides them with significant leeway to tailor their selection based on things like user preferences or bandwidth conditions.

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This integer attribute specifies the start value for numbering the individual list items. Although the ordering type of list elements might be Roman numerals, such as XXXI, or letters, the value of start is always represented as a number. To start numbering elements from the letter "C", use <ol start="3">.

Note: This attribute was deprecated in HTML4, but reintroduced in HTML5.

MDN HTML5

For the elements listed here, this establishes the element's width:

canvas embed iframe img input object video

Note: For all other instances, such as <div>, this is a legacy attribute, in which case the CSS width property should be used instead.

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