Like keyword density, this meta tag has lost favor with the search engines several years ago. Google has stated that it ignores the meta keyword tag. Yahoo appears to recognize this tag to a minor degree and some people have stated that this tag is a good place to put misspellings of keywords but I have seen no proof that Yahoo will rank your website for misspellings found in this tag. I do agree that if
you were trying to rank for misspelled words, this would be a better place to put those words instead of visibly on your website pages.

Personally, I have keywords in my meta keyword tag but it is only because the tag is there, not because I think the tag is giving me any benefit. My own personal experiments with a two word phrase and a four word phrase placed in my own meta keyword tag produced no returned result for my website when those phrases were searched for with and without quotes ( “” ). So, I firmly believe there is no ranking ability from the meta keyword tag. You can include it or you can ignore it. It is entirely up to you.

Very Important: Though Google has stated they ignore the meta keyword tag, never put keywords into your meta keyword tag that do not directly relate to your website’s theme, topic or niche. Also, never repeat the same keywords over and over again in this tag. You do not want any search engine thinking you are trying to spam their results by stuffing keywords into the meta keyword tag.