How do search engines use meta tags?

Part 2 of What are Meta Tags?

We now know what are meta tags (previous post) and that they are really only two that we care about (well most of us, there are some additional ones that should be in a webmasters tool kit). So how do search engines use meta tags?

Keywords meta tag:

It used to be that you could put the keywords you wanted to rank for into the keyword meta tag, and the more the better right? Then you could sit back and consider yourself done with your SEO efforts. This has not been true for a while. Google completely ignores this tag and has for years, and while yahoo and bing probably look at the tag, it is not clear that they give it much weight in determining how to rank your site. Regardless, do not put 30+ keywords into this tag, this is known as keyword stuffing and will only harm your page. Keep it to 10 at most. If you do use adsense or other context driven ads on your site, there is evidence that they use the tag to determine what ads to show.

Description meta tag:

Technically this meta tag doesn’t help your web page rank any better, but it is still important. Why? Because if this tag is set, google will often show it as the snippet underneath the title in the SERPs (search engine results pages) rather than grabbing some random chunk of text off your page. I’ve seen some funny snippets over the years, usually from sites that have no text, so you get a snippet that says “you need flash version xxx to view this site”. Is that going to entice you to click? You can think of your description meta tag as the “welcome” mat to your site. Put together a catchy description (no more than 160 characters as that is all that will show) that will invite your reader to click through to find out more.