Rated 5 out of 5 stars
I got this to work by..
1) Clicking on the install development version
2) Right click on 'add to firefox'
3) Select 'save link as'
4) Choose a folder on your disk to save the cacheviewer-0.7b-fx.xpi file
5) Download 7zip and install if you dont have it.
6) In windows explorer locate the .xpi file you download, right click it and select 7zip-extract to "cacheviewer-0.7b-fx\"
7) Navigate to the folder open install.rdf using notepad and then find the following
change the 4.0b9pre to 4.01 so it becomes
Save the file.
8) Using explorer within the folder itself select all the folder contents , then right click on your mouse , select 7zip- Add to
This should create the file above, finally rename the .zip to .xpi then right click on the file and select open with firefox.