Please provide a screenshot of that.

See this support article. How do I create a screenshot of my problem? It is best to use a compressed image type like PNG or JPG to save the screenshot and make sure that you do not exceed a maximum file size of 1 MB.

Then use the Browse .... button below the Post a Reply text box to upload the screenshot.

Here it is

You can try to disable hardware acceleration in Firefox.

• Options/Preferences -> Advanced -> General -> Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Turning off hardware acceleration made no difference. 3 years ago I found out there is no hardware acceleration for my video chip when mplayer started complaining that, 'Failed to open VDPAU backend libvdpau_i965.so: cannot open shared object file: No such file or directory '

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

firefox -safe-mode doesn't have the problem. Removing all my plugins and extensions made no difference. I use the default theme.

Create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Note that Adobe has released a Shockwave Flash plugin 24.0.0.194 for Linux.

You can download the latest Flash player versions for Firefox via this page:

• https://get.adobe.com/flashplayer/otherversions/

A new profile works, even when I add in all the plugins and extensions. It seems odd that it would get corrupt coincidentally with a new version.

I narrowed down the problem to xulstore.json. Since I want Firefox to start maximized, I imported the main-window record from my old xulstore.json

"main-window":{"sizemode":"normal","screenX":"0","screenY":"0","width":"1356","height":"742"}

That's what causes the problem: starting maximized.

What is the 'right' way to make Firefox start maximized?