Meta elements are the HTML or XHTML element used to provide structured metadata about a Web page. Multiple Meta elements with different attributes are often 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, 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: content, http-equiv, name and 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.
Such elements must be placed as tags in the head section of an HTML or XHTML document.
Meta element used in search engine optimization (SEO)
Meta elements provide information about the web page, which can be used by search engines to help categorize the page correctly.
They have been the focus of a field of marketing research known as search engine optimization (SEO), where different methods are used to provide a user's website with a higher ranking on search engines. Prior to the rise of content-analysis by search engines in the mid-1990s (most notably Google), search engines were reliant on meta data to correctly classify a Web page and webmasters quickly learned the commercial significance of having the right meta element. The search engine community is now divided as to the value of meta tags. 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. Google state they do support for the meta tags "content", "robots", "google", "google-site-verification", "content-type", "refresh" and "google-bot."
Major search engine robots look at many factors when determining how to rank a page of which meta tags will only form a portion. Furthermore, most search engines change their ranking rules frequently. Google have stated they update their ranking rules every 48 hours. Under such circumstances, a definitive understanding of the role of meta tags in SEO is unlikely.
