Meta element
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Meta elements are HTML elements used to provide structured metadata about a web page. Such elements must be placed as tags in the head section of an HTML document.
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[edit] Meta element structure
<!ELEMENT META - O EMPTY -- generic metainformation> <!ATTLIST META %i18n; -- lang, dir, for use with content -- http-equiv NAME #IMPLIED -- HTTP response header name -- name NAME #IMPLIED -- metainformation name -- content CDATA #REQUIRED -- associated information -- scheme CDATA #IMPLIED -- select form of content -- >
[edit] Meta tag use in search engine optimization
Meta elements provide information about a given webpage, most often to help search engines categorize them correctly, and are inserted into the HTML code in the format illustrated above, but are not visible to a user looking at the site.
They have been the focus of a field of marketing research known as search engine optimization (SEO), where different methods are explored to provide a user's site with a higher ranking on search engines. In the mid to late 1990s, 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, as it frequently led to a high ranking in the search engines - and thus, high traffic to the web site.
As search engine traffic achieved greater significance in online marketing plans, consultants were brought in who were well versed in how search engines perceive a web site. These consultants used a variety of techniques (legitimate and otherwise) to improve ranking for their clients.
The keyword tag was popularized by search engines such as Infoseek and AltaVista in 1996 and its popularity quickly grew until it became one of the most commonly used META tags. By late 1997, however, search engine providers realised that information stored in META tags, especially the keyword tag, could be unreliable and misleading, and at worst, could be used to draw users into spam sites. (Unscrupulous webmasters could easily place false keywords into a META tag in order to draw people to their site, whether the content matched these keywords or not.)
Search engines began dropping support for META keywords in 1998, and by the early 2000s, most search engines had veered away from reliance on meta elements, and in July 2002 AltaVista, one of the last major search engines to still offer support, finally stopped including them.
Newer search engines like Google and FAST have never had any support for the META keywords tag.
Some academics, e.g. Zhang & Dimitroff, 2004, have concluded that "webpages with metadata elements achieved better visibility performance than those without metadata elements". However, this may be due to confusion between the HTML <title> tag, which Google does use (and is very important), and HTML <meta...> tags, which Google does not use for indexing. The Director of Research at Google, Monika Henziger, was quoted (in 2002) as saying, "Currently we don't trust metadata" [1]. Techniques have also been developed in order 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. It's more likely that a search engine will ignore the meta keyword element completely, and most do regardless of how many words used in the element.
Some search engines such as Google will display the text specified in the content of the META description tag for a page in their result listings. This allows the webpage author to give a more meaningful description for listings than might be displayed if the search engine was to automatically create its own description based on the page content.
[edit] Meta tag use in social bookmarking
In contrast to completely automated systems like search engines, author-supplied metadata can be useful in situations where the page content has been vetted as trustworthy by a reader. An example usage would be a social bookmarking site that supplies the meta description for the notes and the meta author as a tag. Since the reader is bookmarking the page, it can be assumed he trusts it to some degree. The meta tags act as a convenience for the user.
[edit] Redirects
Meta refresh elements can be used to instruct a web browser to automatically refresh a web page after a given time interval. It is also possible to specify an alternative URL and use this technique in order to redirect the user to a different location. Using a meta refresh in this way and solely by itself will not always work. For Internet Explorer's security settings, under the miscellaneous category, meta refresh can be turned off by the user, therby disabling its redirect ability entirely.
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.
[edit] HTTP message headers
Meta tags of the form <meta http-equiv="foo" content="bar"> can be used to send http headers. For example,
<meta http-equiv="Expires" content="Wed, 21 Jun 2006 14:25:27 GMT">
would tell a browser (or other http client) that the page "expires" on June 21, 2006 and that it may safely cache the page until then.
[edit] Alternative to META elements
An alternative to META elements for enhanced subject access within a web site is the use of a back-of-book-style index for the web site. See examples at the web sites of the Australian Society of Indexers www.aussi.org and the American Society of Indexers [1].
In 1994, ALIWEB, which was likely the first web search engine, also used an index file to provide the type of information commonly found in meta keywords tags.
[edit] References
- ^ Journal of Internet Cataloging, Volume 5(1), 2002
