Rated 4 out of 5 stars

great plugin! i have the same issue, deleting of overlay images does not seem to work (firefox 3.6.2, firebug 1.5.3, pixel perfect 1.5.6, Windows Vista). However i found on Windows you can manually delete the pictures here:
C:\Users\\AppData\Roaming\Mozilla\Firefox\Profiles\\extensions\pixelperfectplugin@openhouseconcepts.com\chrome\pixelperfect\content

Sebastian

This review is for a previous version of the add-on (1.5.6).