Tags defining website title, description and keywords used for locating engine spiders or crawlers for, fast indexing in search engines, to appear on organic listing by, searching for any keywords or key phrase for a website are called Meta Tags. Meta tags are available in the HEAD section and are not displayed to the end user unless the source code of the page is viewed. Use of tags include showing keywords and phrases to the search engines and online visitors related to the services offered as well as support webmasters in providing information to a browser, search engine, or automated program (i.e., robot).
There are several meta tags, here are a few important ones to list
(a) Meta Description Tag: Title should not be repeated in this tag as it is used as a short page description in search engine listings. The description in Meta Description tag should not exceed 150-200 characters using the specific keyword at least once or twice if it fits. Common synonyms and one or two of the most important general keywords should be included in the Meta Description tag.
(b) Meta Keywords Tag: The search engine is informed about the important keywords on the page, and their usage to enable people find you when they search. Meta Keywords tag can include the specific keyword, one or two most important general keywords, some of the common upper/lower case variations of the keyword, synonyms and related words including misspellings. Nowadays, however, major search engines like Google and Alta Vista ignore this tag, and the Meta Keywords Tag no longer has the significance it used to have in the early days of the web.
(c) Meta Robots Tag: Instructions to web-indexing robots, guiding whether or not to index the page and also follow the links that are on it are included in this Meta Robots tag. The Meta Robots tag is used to prevent the search engines from spidering the meta refresh tags or other risky techniques pages, as these are often used for spamming, to prevent penalization by search engines.
(d) Meta Revisit Tag: The frequency relating to the revisit of a search engine or robot to the Web site for re-indexing is mentioned in this tag. The use of Meta Revisit Tag includes controlling search engine placement of Web sites which change content on a regular basis.
(e) Meta Expires Tag: The browser is forced not to cache a page, to enable load a new copy from the server each time the page is viewed through this Meta Expires tag. To use Meta Expires Tag set the expiry date to 0 and to make a page expire at a specific time in the future, spell it out in Greenwich Mean Time.
(f) Meta Refresh Tag: Users are automatically sent to another URL, on elapsing of a specified amount of time through this Meta Refresh Tag. For using Meta Refresh Tag the new destination URL is placed after the number of seconds to delay and a semicolon.
Although meta tags are not substantial, and affective in controlling search engines indexing and listing of page, it is a good idea to add these tags to the page as it requires very little effort. For the Meta Tags to be effective and consistently attract search engines, the meta tags must be placed on each and every page of the website no matter how many pages are there.