Is this the Alexa Toolbar?
At first, this toolbar used methods that a standard website would use to calculate the Alexa ranking. The toolbar became so popular, however, that Alexa contacted us and worked with us to make this toolbar a bonified - Alexa recommended - toolbar. So even though this toolbar was not created by Alexa, it is now considered one of their officially supported ones.
What makes this much better than the Alexa toolbar that they put out is that this also shows the PageRank of every site you visit as well. Also, you get some very useful SEO tools with this add-on that Alexa simply does not offer.