Common Meta Tags
The most common reason to use meta tags is to provide a description of the page for search engines. This is done with the
<meta name="description"> tag. The description tag provides a short (typically 400 characters or less) description of the page that search engines use below the linked title. A good description can entice readers onto your web page.
A related meta tag is the
<meta name="keywords"> tag. This allows the page author to define keywords that are related to the page content. Some search engines use this tag to populate their indexes and some do not.
A final meta tag that is used quite often is the meta refresh tag. This tag will redirect the web browser to a new URL or refresh the current page to provide some dynamic content.
Meta Tags are Not Required
A web page can be posted that is valid, readable, and found by search engines without any meta tags at all. As I mentioned above, many search engines don't use the keywords meta tag. And if you leave off the description, most search engines will simply grab some text from the page content itself.
I recommend using the meta description tag and skipping the rest. This gives you the most efficient use of your time while optimizing for the major search engines (Google, Yahoo!, and Bing). Then you can decide to use other meta tags (like author, copyright, etc.) as you need them on your documents. You will probably discover that you don't really need them.