Meta element used in search engine optimization
Meta elements provide information about the web page, which can be used by search engines to help categorize the page correctly.
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. The keywords attribute
Unlike the 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. The language attribute
The robots attribute, supported by several major search engines, 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 one of the best options for preventing search engines from indexing content of a website. Additional attributes for search engines
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” >
MSN and Live Search (via bingbot, previously msnbot):
<meta name=”bingbot” content=”noodp” >
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 robots-nocontent tag:excluded content excluded content
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” >