DO YOU KNOW WHAT META TAGS ARE?
The two most commonly discussed are keywords meta tag and description meta tag. There is also the title tag, which is the most important in this day and age.
KEYWORD META TAGS
In the early days of search engines this was an important way of telling the engine what the web page was about but it quickly became abused since it was possible to place words into this tag just for ranking purposes.
Take a look at almost any site and take note of the very many keywords stuffed into this tag. No web page can possibly be about all those keywords! Here is an example. This is a bad SEO strategy, your web page should be about one or two topics, and therefore should never have more than 5 keywords in the meta keywords tags.
Google and most other international search engines now seem to ignore this meta tag for ranking purposes (but beware maybe not for ever). I include this meta tag as a matter of routine.
Inktomi (now owned by Yahoo) and MSN as well these days does consider keyword tags.
DESCRIPTION META TAG
Take a look at any SERP from Google. Here is an example of a description tag from one of my sites.
The informational text below the Title link on SERPs used to come from the meta description tag. Google generally has stopped using this tag because once more it was becoming abused. Instead of looking at the description tag for this information Google now returns one or more snippets of text from the body reasonably close to an occurrence of the query word/phrase used to return the SERP.
It has been reported recently that Google is using this particular tag again. Other major search engines do use the tag. I include it as a matter of routine and always ensure it contains my keyword, towards the start of the sentence.
ROBOTS META TAG
A special tag is called the robots tag and is used to prevent search engine spiders indexing a particular page or site. There are legitimate uses for this tag (imagine a price list posted for special purposes and you do not want the whole world to see it) but it is also one used a lot by spammers.