This past July on WebmasterWorld, Duane Forrester, a senior product manager at Bing said: “I’ll make this statement: meta keywords is a signal. One of roughly a thousand we analyze. Getting it right is a nice perk for us, but won’t rock your world. Abusing meta keywords can hurt you.”
Based on this information, some questions to ask are should you use the meta keywords tag and if so, what are the best ways of optimizing it without sending off any spam signals to search engines? Although Google has indicated it no longer uses the meta keywords tag as a ranking signal, and Yahoo and Bing also downplay its importance in its ability to help a site rank, we still like to recommend using it since other less popular search engines are use it as a ranking signal.
In terms of best practices, I’d generally recommend using between 3-5 keywords per page in the field. It’s very important to use keywords that are accurate of what is on the page as well, make sure not to throw irrelevant keywords in the field that aren’t descriptive of what is on the page. Doing so sets off an immediate spam signal to search engines. Also don’t rewrite the same keyword over and over, which we’ve come across on some sites, doing so will also set off spam signals.