why page rank of my site has changed so much?

i checked my site (http://www.reviewtaxsoftwares.com) last night using keyword (best tax software 2008), it was on google first page position #4, but this morning, I tried the same keyword, it is not even showing up in the first 100 result. Very strange and frustrated!



Any thoughts what is causing it? I've added a google xml sitemap couple days, will that be an issue?



Thanks

Is it possible that your use of the trademark Turbo Tax in your keywords metatag may have been noticed by Turbo Tax people and they filed a spamreport@google.com to have your website/domain name removed from google.com's database. Understandably, no one is allowed to use trademarks as keywords on a webpage without showing of the registry mark. You should contact google editors via an email query if that is the case.

Good luck!