Quadrille - 1:50 pm on Aug 10, 2008 (gmt 0)

Meta keywords do not have any effect on Google rankings, according to Google, and have not for years.

But that does not mean that the keyword tag is ignored.

It may hold evidence of keyword stuffing, or other deprecated behaviours, and they will be noted.

If you use keyword tags, then you should use them appropriately.

Having said all that, I think your serps drop is entirely coincidental. Look elsewhere for the cause.

The only way I can envisage keywords contributing to a drop, is if someone successfully reported you for keyword stuffing. But that is pretty unlikely.

Go back and review actions you took previously - up to a few months ago - and double check your outgoing links for danger signs.