Do you mean where it ranks in the serps (search engine results pages) or as in Google Page Rank? For the former, there are software tools that you can use to monitor your keywords rankings - search google on 'keyword tracker tool'. if you mean the latter, you need to download the Google Toolbar to view your site's page rank - bear in mind, this can be up to 3 months out of date, as Google updates page rank approximately 4 times per year.
Check out your Google sitemap account and you wll see if you have incoming traffic from certain keywords