Rated 5 out of 5 stars
This is one of the most useful tools when creating an optimal website.
This add-on is reporting "Unknown" size for all pages once I installed this on Windows 7. This happens for all websites also. Is there any known issues with 7?
I'm not aware of any specific problem on Windows 7. The size is "Unknown" when a resource isn't in the browser's cache; this happens for all files loaded over https.