The Meta Description tag is has some value with certain search engines as to how your site will be described in a search for your company name or domain name. This is an example in which the searcher does not use an exact keyword. This occurs when someone searches for your exact company name. This is the only time you will see a search engine really using something from the meta family other then the title tag. It is a good idea to place some informative and inviting text in this tag line about your company. Lets look at a good Meta Description tag that was made for a Widget website.

Widget warehouse USA in the number one dealer of widgets in the world. We carry the most complete selection of widgets available on the Internet for purchase. At Widget Warehouse we are your one stop shop for all your widget needs. At Widget Warehouse, customer service is our number one priority. If you plan on buying a blue Widget, red Widget or green Widget, shop on line with confidence in our totally secure shopping cart. Nobody sell more Widgets then Widget Warehouse!

This Meta description uses the chosen Keyword quite a bit and describes the web site well. Unlike the Meta Keywords, using your Keyword here is helpful and will help your rankings.