Meta elements are the HTML or XHTML
<meta … > 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:
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.
An example of the use of the
In one form,
meta elements can specify HTTP headers which should be sent before the actual content when the HTML page is served from Web server to client. For example:
<meta http-equiv="Content-Type" content="text/html" >
This specifies that the page should be served with an HTTP header called 'Content-Type' that has a value 'text/html'. In the general form, a
meta element specifies
name and associated
content attributes describing aspects of the HTML page. For example:
<meta name="keywords" content="wikipedia,encyclopedia" >
In this example, the
meta element identifies itself as containing the 'keywords' relevant to the document, Wikipedia and encyclopedia. Meta keywords are no longer used by any major search engine, in fact keyword stuffing can negatively affect your rankings.
Meta tags can be used to indicate the location a business serves:
<meta name="zipcode" content="45212,45208,45218" >
In this example, geographical information is given according to ZIP codes.
Default charset for plain text is simply set with meta:
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" >
Meta element used in search engine optimization
Meta elements provide information about a given Web page, most often to help search engines categorize them correctly. They are inserted into the HTML document, but are often not directly visible to a user visiting 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 website.
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 website. These consultants used a variety of techniques (legitimate and otherwise) to improve ranking for their clients.
Meta elements have significantly less effect on search engine results pages today than they did in the 1990s and their utility has decreased dramatically as search engine robots have become more sophisticated. This is due in part to the nearly infinite re-occurrence (keyword stuffing) of meta elements and/or to attempts by unscrupulous website placement consultants to manipulate (spamdexing) or otherwise circumvent search engine ranking algorithms.
While search engine optimization can improve search engine ranking, consumers of such services should be careful to employ only reputable providers. Given the extraordinary competition and technological craftsmanship required for top search engine placement, the implication of the term "search engine optimization" has deteriorated over the last decade. Where it once implied bringing a website to the top of a search engine's results page, for some consumers it now implies a relationship with keyword spamming or optimizing a site's internal search engine for improved performance.
Major search engine robots are more likely to quantify such extant factors as the volume of incoming links from related websites, quantity and quality of content, technical precision of source code, spelling, functional v. broken hyperlinks, volume and consistency of searches and/or viewer traffic, time within website, page views, revisits, click-throughs, technical user-features, uniqueness, redundancy, relevance, advertising revenue yield, freshness, geography, language and other intrinsic characteristics.
keywords attribute was popularized by search engines such as Infoseek and AltaVista in 1995, and its popularity quickly grew until it became one of the most commonly used
meta elements. By late 1997, however, search engine providers realized that information stored in
meta elements, especially the
keywords attribute, was often unreliable and misleading, and at worst, used to draw users into spam sites. (Unscrupulous webmasters could easily place false
keywords into their
meta elements in order to draw people to their site.)
Search engines began dropping support for metadata provided by the
meta element in 1998, and by the early 2000s, most search engines had veered completely away from reliance on
meta elements. In July 2002, AltaVista, one of the last major search engines to still offer support, finally stopped considering them.
No consensus exists whether or not the
keywords attribute has any effect on ranking at any of the major search engines today. It is speculated that it does, if the keywords used in the
meta can also be found in the page copy itself. With respect to Google, thirty-seven leaders in search engine optimization concluded in April 2007 that the relevance of having your keywords in the
keywords is little to none and in September 2009 Matt Cutts of Google announced that they are no longer taking keywords into account whatsoever. However, both these articles suggest that Yahoo! still makes use of the keywords meta tag in some of its rankings. Yahoo! itself claims support for the keywords meta tag in conjunction with other factors for improving search rankings. In Oct 2009 Search Engine Round Table announced that "Yahoo Drops The Meta Keywords Tag Also" but informed us that the announcement made by Yahoo!'s Senior Director of Search was incorrect. In the corrected statement Yahoo! Senior Director of Search states that "...What changed with Yahoo's ranking algorithms is that while we still index the meta keyword tag, the ranking importance given to meta keyword tags receives the lowest ranking signal in our system.... it will actually have less effect than introducing those same words in the body of the document, or any other section." In Sept 2012, Google announced that they will consider Keyword Meta tag for news publishers. Google said that this may help worthy content to get noticed, the syntax of the news meta keyword has subtle difference from custom keyword meta tag, it is denoted by "news_keywords", while custom keyword meta tag is denoted by "keywords".
keywords attribute, the
description attribute is supported by most major search engines, like Yahoo! and Bing, while Google will fall back on this tag when information about the page itself is requested (e.g. using the related: query). The
description attribute provides a concise explanation of a Web page's content. This allows the Web page authors to give a more meaningful description for listings than might be displayed if the search engine was unable to automatically create its own description based on the page content. The description is often, but not always, displayed on search engine results pages, so it can affect click-through rates. Industry commentators have suggested that major search engines also consider keywords located in the
description attribute when ranking pages. W3C doesn't specify the size of this description meta tag, but almost all search engines recommend it to be shorter than 155 characters of plain text.
language attribute tells search engines what natural language the website is written in (e.g. English, Spanish or French), as opposed to the coding language (e.g. HTML). It is normally an IETF language tag for the language name. It is of most use when a website is written in multiple languages and can be included on each page to tell search engines in which language a particular page is written.
robots attribute, supported by several major search engines,[not in citation given] controls whether search engine spiders are allowed to index a page, or not, and whether they should follow links from a page, or not. The attribute can contain one or more comma-separate values. The
noindex value prevents a page from being indexed, and
nofollow prevents links from being crawled. Other values recognized by one or more search engines can influence how the engine indexes pages, and how those pages appear on the search results. These include
noarchive, which instructs a search engine not to store an archived copy of the page, and
nosnippet, which asks that the search engine not include a snippet from the page along with the page's listing in search results.
Meta tags are not the best option to prevent search engines from indexing content of a website. A more reliable and efficient method is the use of the robots.txt file (robots exclusion standard).
Additional attributes for search engines
The search engines Google, Yahoo! and MSN use in some cases the title and abstract of the Open Directory Project (ODP) 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 ODP 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. Google followed in July 2006 and Yahoo! in October 2006.
The syntax is the same for all search engines who support the tag.
<meta name="robots" content="noodp" >
Webmasters can decide if they want to disallow the use of their ODP listing on a per search engine basis
<meta name="googlebot" content="noodp" >
<meta name="Slurp" content="noodp" >
<meta name="bingbot" content="noodp" >
Yahoo! puts content from their own Yahoo! directory next to the ODP listing. In 2007 they introduced a meta tag that lets web designers opt-out of this.
If you add the
NOYDIR tag to a page, Yahoo! won't display the Yahoo! Directory titles and abstracts.
<meta name="robots" content="noydir" > <meta name="Slurp" content="noydir" >
Yahoo! also introduced in May 2007 the attribute value:
class="robots-nocontent". This is not a meta tag, but an attribute and value, which can be used throughout Web page tags where needed. Content of the page where this attribute is being used will be ignored by the Yahoo! crawler and not included in the search engine's index.
Examples for the use of the
<div class="robots-nocontent">excluded content</div> <span class="robots-nocontent">excluded content</span> <p class="robots-nocontent">excluded content</p>
Google does not use HTML keyword or meta tag elements for indexing. 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."  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. It is more likely that a search engine will ignore the meta keyword element completely, and most do regardless of how many words are used in the element.
Google does, however, use meta tag elements for displaying site links. The title tags are used to create the link in search results:
<title>Site name - Page title - Keyword description</title>
The meta description often appears in Google search results to describe the link:
<meta name="description" content="A blurb to describe the content of the page appears here" >
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. Auto refreshing via a META element has been deprecated for more than ten years, and recognized as problematic before that.
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.
HTTP message headers
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.
An alternative to
meta elements for enhanced subject access within a website is the use of a back-of-book-style index for the website. See the American Society of Indexers website for an example.
In 1994, ALIWEB, also used an index file to provide the type of information commonly found in meta keywords attributes.
- Meta refresh, a deprecated meta element
- RDFa, attribute level extensions to XHTML, for embedding metadata
- Resource Description Framework (RDF)
- Statistic (June 4, 1997), META attributes by count, Vancouver Webpages, retrieved June 3, 2007
- Danny Sullivan (October 1, 2002), Death Of A Meta Tag, SearchEngineWatch.com, retrieved June 03, 2007
- "In 2007, 37 leaders in search engine optimisation concluded that having keywords in the keywords attribute is little to none." Sanger.nu blog, September 9 2008, retrieved August 2 2011
- "Google does not use the keywords meta tag in web ranking" Google Webmaster Central Blog, September 21, 2009, retrieved September 21, 2009
- Yahoo! FAQs, How do I improve the ranking of my web site in the search results?, Yahoo.com, retrieved November 12, 2008
- "Yahoo Drops The Meta Keywords Tag Also" SEO Roundtable, October 8, 2009, retrieved April 22, 2011
- "Yahoo's Senior Director of Search Got It Wrong, Yahoo Uses Meta Keywords Still" SEO Roundtable, October 16, 2009, retrieved April 22, 2011
- Danny Sullivan, How To Use HTML Meta Tags, Search Engine Watch, December 5, 2002
- 1 Website Designer Using language metatags in websites February 19, 2008
- Vanessa Fox, Using the robots meta tag, Official Google Webmaster Central Blog, 3/05/2007
- Danny Sullivan (March 5, 2007),Meta Robots Tag 101: Blocking Spiders, Cached Pages & More, SearchEngineLand.com, retrieved June 3, 2007
- Betsy Aoki (May 22, 2006), Opting Out of Open Directory Listings for Webmasters, Live Search Blog, retrieved June 3, 2007
- Vanessa Fox (July 13, 2006), More control over page snippets, Inside Google Sitemaps, retrieved June 3, 2007
- Yahoo! Search (October 24, 2006), Yahoo! Search Weather Update and Support for 'NOODP', Yahoo! Search Blog, retrieved June 3, 2007
- Yahoo! Search (February 28, 2007), Yahoo! Search Support for 'NOYDIR' Meta Tags and Weather Update, Yahoo! Search Blog, retrieved June 3, 2007
- Yahoo! Search (May 02, 2007), Introducing Robots-Nocontent for Page Sections, Yahoo! Search Blog, retrieved March 23, 2013
- Greta de Groat (2002). "Perspectives on the Web and Google: Monika Henzinger, Director of Research, Google", Journal of Internet Cataloging, Vol. 5(1), pp. 17-28, 2002.
- W3CTechniques for Web Content Accessibility Guidelines W3C Working Draft 26-Feb-1999
- Techniques for Web Content Accessibility Guidelines W3C Working Draft 17-Feb-1999
- Accessibility.blockautorefresh mozillaZine, archived June 2, 2009 from the original
- W3C Recommendation (May 5, 1999), Web Content Accessibility Guidelines 1.0 - Guideline 7. W3.org, retrieved September 28, 2007
- W3C Recommendation (December 24, 1999), HTML 4.01 Specification. W3.org', retrieved July 24, 2012
- Stack Overflow, meta http-equiv - is it sent as part of an HTTP header, or does the client parse the body for meta tags?, from a London Web Standards tech talk.