We are often asked about the importance and role of the meta keyword tag. Here is a little information:

• The meta keywords tag is not considered by Google at all
• The meta keywords tag is not considered by Bing at all
• The meta keywords tag is barely considered by Yahoo, and for categorisation purposes only
• Yahoo will be using the Bing search technology later this year so even the very marginal benefit offered by Yahoo is soon to be removed

So, best practice says add upto 10 comma-separated keyphrases in the meta keywords tag, but if you don’t it will make very little difference to your rankings.