Normally, I'd say to check for updates to your graphics driver. However, there's no update available for your card.

• http://support.amd.com/en-us/download

Try the following.

1. Type about:config into the address bar and press Enter.
2. To bypass the warning, press the big button labeled "I'll be careful, I promise!".
3. In the lower pane, right-click and choose New then Boolean.
4. As the preference name, enter layout.paint_rects_separately and as the value choose true
5. Restart Firefox.

If the above doesn't help, disable hardware acceleration.

1. Click the ≡ Menu Button and choose Options.
2. Click the Advanced icon.
3. Click the General tab.
4. Uncheck "Use hardware acceleration when available".
5. Restart Firefox.

This issue appears to be specific to old ATI graphics drivers and Firefox 33.0b7.

• http://forums.mozillazine.org/viewtopic.php?f=23&t=2872877

Thanks for the reply.

layout.paint_rects_separately didn't fix it unfortunatly and I've already tried disabling HWA. I even reset Firefox and it still does it but in safe mode it's fine? it only started happening around 3 days ago and I've not got any updates for any hardware/software in a while either.

I've added images to help explain what's happening in better detail:

If I scroll on a subreddit the black boxe just keeps moving too, and any website with a slider shows black backgrounds and black boxes whenever there's an animation, I've even getting black boxes whilst typing here, as show in the attachments.

You did close and restart Firefox after disabling hardware acceleration in Firefox?

If it works in safe mode, then the problem is one of the add-ons or one of the settings.

I did close and restart firefox when trying to HWA fix yeah, also I have no addons.

Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

• Download the full Firefox installer and save the file to the desktop
  https://www.mozilla.org/en-US/firefox/all.html

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

• Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then also create a new profile.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

Thanks for all the excellent advice! uninstalling, removing the program directory and then reinstalling worked :)