Andem - 7:39 pm on Jan 13, 2011 (gmt 0)
>> If you use an ad blocker, enable PageRank in the Google Toolbar, and surf your own site it is pretty easy to significantly influence the Webmaster Tools performance measure.
I agree with bumpski here! I've been away from home over the past 5 weeks and surfing my own site on some very crappy Internet connections (read: unsecured W-LAN from across the street). This in its self has caused my site performance to really take a dive last time I checked.