Meta elements are tags used in HTML and XHTML documents to provide structured metadata about a Web page.
They are part of a web page's
head section. Multiple Meta elements with different attributes can be used on the same page. Meta elements can be used to specify page description, keywords and any other metadata not provided through the other
head elements and attributes.
The meta element has two uses: either to emulate the use of an HTTP response header field, or to embed additional metadata within the HTML document.
With HTML up to and including HTML 4.01 and XHTML, there were four valid attributes:
scheme. Under HTML 5 there are now five valid attributes,
charset having been added.
http-equiv is used to emulate an HTTP header, and
name to embed metadata. The value of the statement, in either case, is contained in the
content attribute, which is the only required attribute unless
charset is given.
charset is used to indicate the character set of the document, and is available in HTML5.
The two distinct parts of the elements are:
Additionally, enterprise search startup Swiftype considers meta tags as a mechanism for signaling relevancy for their web site search engines, even introducing their own extension called Meta Tags 2.
The W3C suggests that user agents should allow users to disable it, otherwise META refresh should not be used by web pages. For Internet Explorer's security settings, under the miscellaneous category, meta refresh can be turned off by the user, thereby disabling its redirect ability. In Mozilla Firefox
The W3C suggests that user agents should allow users to disable it, otherwise META refresh should not be used by web pages. For Internet Explorer's security settings, under the miscellaneous category, meta refresh can be turned off by the user, thereby disabling its redirect ability. In Mozilla Firefox it can be disabled in the configuration file under the key name "accessibility.blockautorefresh".
Many web design tutorials also point out that client-side redirecting tends to interfere with the normal functioning of a Web browser's "back" button. After being redirected, clicking the back button will cause the user to go back to the redirect page, which redirects them again. Some modern browsers seem to overcome this problem however, including Safari, Mozilla Firefox and Opera.
Auto-redirects via markup (versus server-side redirects) are not in compliance with the W3C's - Web Content Accessibility Guidelines (WCAG) 1.0 (guideline 7.5).
Meta elements of the form
<meta http-equiv="foo" content="bar"> can be used as alternatives to HTTP headers. For example,
<meta http-equiv="expires" content="Wed, 21 June 2006 14:25:27 GMT"> would tell the browser that the page "expires" on June 21, 2006 at 14:25:27 GMT and that it may safely cache the page until then. The HTML 4.01 specification optionally allows this tag to be parsed by HTTP servers and set as part of the HTTP response headers, but no web servers currently implement this behavior. Instead, the user agent emulates the behavior for some HTTP headers as if they had been sent in the response header itself.