Whenever checking backlinks I have always noticed there is a huge difference between the backlinks reported by Google and Yahoo. What causes this difference? Isn't a link a link? Is there a way to work on bringing the links up for Yahoo if one wanted to level them out? Thanks for your comments in advance!
There is a difference as to what Google, Yahoo, and MSN consider valid links. Much of it is effected by how their spiders and algorithm view nofollow links. Also, each hasn't indexed all the same pages, so some backlinks won't be found. Google supposedly won't display all the links to prevent website competitors from seeing one another's backlinks. You can better find the backlinks for Google in Webmaster Tools.