You may have zoomed out at some point, after which your preference was remembered. Hold down Ctrl and press 0 (that's the number zero) to reset the zoom level.

Also see Websites look wrong or appear differently than they should.

Thanks for the reply. As I mentioned, only addons.mozilla has this problem. All other web pages - including the rest of mozilla.org - are just dandy. This issue has presented itself on the last two machines that I installed firefox on, both with different operating systems. Attached is a screenshot.

Any other ideas?

So, View > Zoom > Reset doesn't help?

• Press the F10 key or tap the Alt key to bring up the hidden "Menu Bar" temporarily.

You can rename the content-prefs.sqlite file to content-prefs.sqlite.old (or delete the file) in the Firefox profile folder to reset the page zoom for all websites.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux:Open Directory; Mac:Show in Finder)

You can remove all data stored in Firefox from a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History > Show All History" or "View > Sidebar > History") or via the about:permissions page.

Using "Forget About This Site" will remove all data stored in Firefox from that domain like bookmarks, cookies, passwords, cache, history, and exceptions, so be cautious and if you have a password or other data from that domain that you do not want to lose then make a note of those passwords and bookmarks.

You can't recover from this 'forget' unless you have a backup of the affected files.

It doesn't have any lasting effect, so if you revisit such a 'forgotten' website then data from that website will be saved once again.