For the last few months I have noticed a fairly substantial decline in my Alexa rating despite an upturn in traffic after the Christmas holidays. The traffic hasn't been as high as during the PageRank updates in October 2007, but certainly higher than the average for most of last year, even factoring in some downturn in Stumbleupon traffic.
Quantcast provide real data because I am Quantified with their code embedded in every page
We can compare that data with Alexa
I have also had some incompatibility problems with a few users of Internet Explorer with some of the Javascript widgets, though the errors
