SenSEO is a Firebug FireFox addon (this means you have to install FireBug to use it) checking important on-page-SEO criteria and calculating a grade of how good the current site fulfills these criteria. The tool adds one extra tab to FireBug window which allows to inspect the current page. The first thing to do is to identify a keyword (or a key phrase) to inspect the page against it. Just type in the search box and click “Inspect SEO Criteria.”
http://www.searchenginejournal.com/on-page-diagnosis-with-senseo-firefox/18227/