Hello,

The Refresh feature (called "Reset" in older Firefox versions) can fix many issues by restoring Firefox to its factory default state while saving your bookmarks, history, passwords, cookies, and other essential information.

Note: When you use this feature, you will lose any extensions, toolbar customizations, and some preferences. See the Refresh Firefox - reset add-ons and settings article for more information.

To Refresh Firefox:

1. Open the Troubleshooting Information page using one of these methods:
   • Click the menu button , click help and select Troubleshooting Information. A new tab containing your troubleshooting information should open.
   • If you're unable to access the Help menu, type about:support in your address bar to bring up the Troubleshooting Information page.
2. At the top right corner of the page, you should see a button that says "Refresh Firefox" ("Reset Firefox" in older Firefox versions). Click on it.
3. Firefox will close. After the refresh process is completed, Firefox will show a window with the information that is imported.
4. Click Finish and Firefox will reopen.

Did this fix the problem? Please report back to us!

Thank you.

I should have said that the problem is not limited to FF, but also occurs in Thunderbird, and that my system is Kubuntu 14.04.

This has been an ongoing and unresolved issue in Linux for the past two years. I posted about this here, in Mozillazine, as well as created a bug report in Bugzilla. Resetting Firefox does not resolve it and has nothing to do with this. When the problem first noticed, I was using Xubuntu 14.04. Now I am using Linux Mint 18.2 and regardless of the theme I use, there is no change. Currently I have two versions of Firefox installed, 52.5.0 ESR and 57.0 and the issues are the same. Please see attached image

Thanks to responders. I have found a solution! Just a shame I didn't find it 2 years ago...

Tested only on Kubuntu 14.04 using FF 57.0 (64-bit) and Thunderbird 52.4.0 (64-bit), although it seems as though it should be more widely effective.

System Settings->Application Appearance/Colours:Colours.Tooltip Background : Set to something-other-than-black.

This fix took me about 1 minute, if I don't include the many hours over the past 2 years :(

Thanks for the reply, unfortunately, the solution in Kubuntu needs to be adapted to Linux Mint because the system utilities are not the same, I posted this issue in the Mint Forum with a link back to this post.

What is interesting is that no one at Mozilla provides information on the source of the problem, although Bugzilla has several bug reports on the subject. This is after reporting this some two years ago.

Finally resolved the issue by adding the following to the userChrome.css

tooltip {

   -moz-appearance: none !important;
   background-color: #BDF0F7 !important;
   color: #000000 !important;
   padding: 2px 12px;

}

courtesy of a mozillazine user

http://forums.mozillazine.org/viewtopic.php?f=38&t=3035858

Tx, ineuw. It didn't work for me. I created a directory "chrome" in "~/.mozilla/firefox/xxx", in which I created "userChrome.css", containing the following:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); tooltip {

  -moz-appearance: none ;
  background-color: #BDF0F7 ;
  color: #000000 ;
  padding: 2px 12px;

}

I'm sure I did something wrong :(

Hi 6by9, I was told that "! important" is necessary to override previous settings and would not work without it.

Tx, ineuw - who'd have guessed it! That had the effect that hovering over tabs, reload and the forward/back icons are now in black on pale blue and therefore legible. Others are still illegible - eg anything in the address box, and home and menu icons. If I combine your fix and my workaround, I can now see all tooltips.