goodroi - 1:18 pm on Feb 28, 2010 (gmt 0)
Each search engine measures backlinks differently. Also search engines do not always give credit for every single backlink you have pointing to your site. This could be because the linking page is poor quality or has yet to be re-crawled by the search engine.
To find out how many backlinks the search engines think your website has you need to perform a backlink search with each search engine. Google shares this information only with site owners when they log into Google's Webmaster Central. For Yahoo you can use Yahoo's Site Explorer.