Install CSS Viewer For Firefox 3.5.XCSSViewer is a very handy add on for Firefox, which shows the css parameters of any element in a website. If you use it once then you cannot live without it.
The bad news are that it is not compatible with the Firefox 3.5.* version, and from what I can understand there are no plans for an update.
The good news are that there is a really easy way to install it and make it work perfect in Firefox 3.5.*
1. Copy the following address to another browser than Firefox (so that the pop up installation window will not come out)
if you do not have any other browser installed go to
2. Download the file cssviewer-1.0.3-fx.xpi
3. Use 7-zip (or any other extractor) to open it and extract it
4. Open install.rdf with notepad (I used Notepad++ to find easily the line I must change)
5. On line 18 you see 3.0.* you must change it to 3.5.*
6. Save the file and select all the files you extracted and make a zip file
7. Now you must rename the zip file including the zip extension to cssviewer-1.0.3-fx.xpi (it will prompt you if you are sure you want to change the file name extension and you must click yes)
8. Now drag n’ drop the xpi file to Firefox 3.5.* and the installation window will pop up. Install it normally ;)
I have checked it and it works great in Firefox 3.5.1