Meta elements are tags used in HTML and XHTML documents to provide structured metadata about a Web page.
[1] 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.
meta elements can specify HTTP headers which should be sent before the actual content when the HTML page is served from the web server to the client.
For example: as an alternative to the response header Content-Type: to indicate the media type and, more commonly needed, the UTF-8 character encoding.
Prior to the rise of content-analysis by search engines in the mid-1990s (most notably Google), search engines were reliant on metadata to correctly classify a Web page and webmasters quickly learned the commercial significance of having the right meta element.
Some claim they have no value, others that they are central, while many simply conclude there is no clear answer but, since they do no harm, they use them just in case.
Major search engine robots look at many factors when determining how to rank a page of which meta tags will only form a portion.
[3] No consensus exists whether or not the keywords attribute has any effect on ranking at any of the major search engines today.
itself claims support for the keywords meta tag in conjunction with other factors for improving search rankings.
"[8] In Sept 2012, Google[9] announced that they will consider Keyword Meta tag for news publishers.
It used to be standard SEO practice to include the primary and the secondary keywords in the title for better ranking.
and Bing, while Google will fall back on this tag when information about the page itself is requested (e.g. using the related: query).
W3C doesn't specify the size of this description meta tag, but almost all search engines recommend it to be shorter than 160 characters of plain text.
User-agents can (and do) use language information to select language-appropriate fonts, which improves the overall user experience of the page.
and MSN used in some cases the title and abstract of the DMOZ (aka Open Directory Project) listing of a website for the title and/or description (also called snippet or abstract) in the search engine results pages (SERP).
To give webmasters the option to specify that the Open Directory Project content should not be used for listings of their website, Microsoft introduced in May 2006 the new "NOODP" value for the "robots" element of the meta tags.
Webmasters can decide if they want to disallow the use of their ODP listing on a per search engine basis Google: Yahoo!
The Director of Research at Google, Monika Henzinger, was quoted (in 2002) as saying, "Currently we don't trust metadata because we are afraid of being manipulated.
"[20] Other search engines developed techniques to penalize Web sites considered to be "cheating the system".
For example, a Web site repeating the same meta keyword several times may have its ranking decreased by a search engine trying to eliminate this practice, though that is unlikely.
For Internet Explorer's security settings, under the miscellaneous category, meta refresh can be turned off by the user, thereby disabling its redirect ability.