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I've noticed, that sometimes in the left upper corner of the Firefox GUI there are "scratches" visible.

Does anybody know where those scratches are coming from and why?

Here are screenshots:
screenshot1 screenshot2

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I am using OSX Snow Leopard and Firefox in version 13.0.1 (just updated to 14.0.1, will see, whether this behaviour remains the same). – Shachmuta Jul 22 '12 at 15:01
Are you using a HiDPI resolution (e.g. Retina MacBook Pro)? – Daniel Beck Jul 22 '12 at 17:18
No, but I have external display with resolution of 1920x1200 connected via "thunderbolt-to-DisplayPort"-cable, but I've never had any similar rendering issue. It's an early 2011 13" MBP, if that is of any concern. – Shachmuta Jul 22 '12 at 17:37
I do not have a Mac. But if you can make a screenshot of such an issue then the issue is actually present in the video ram of the display adapter. So I would look towards (hostile?) software present in the system itself. – Niels Basjes Jul 25 '12 at 21:25
At what point do they disappear again? If you drag the window around, if you minimize/restore the window? Never? At what point do they appear? – Bobby Aug 13 '12 at 11:14

I found three questions about this on the Mozilla support forum.

So you aren't alone. There doesn't seem to be one solution, but a series of them.

So, to troubleshoot it, try the following in order of work:

  1. Check if Firefox needs to be updated. Update it to the latest version.
  2. Possibly an extension is acting up. Start Firefox in Safe Mode so that no extensions are running. If the lines are gone, it's probably an extension. You could then disable and enable extensions one by one to isolate the culprit.
  3. Reset Firefox. I'd do this one last as it clears out some of your settings.

Hope something here helps. If one does, leave a comment so we can all know what the fix is.

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The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences. To Reset Firefox do the following:

  1. Go to Firefox > Help > Troubleshooting Information.
  2. Click the "Reset Firefox" button.
  3. Firefox will close and reset. After Firefox is done, it will show a window with the
  4. information that is imported. Click Finish. Firefox will open with all factory defaults applied.

If this doesn't fix the problem, try to download and install the newest Firefox. This will also resolve the problem.

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Try opening Firefox in Safe Mode. If the issue is not present in Safe Mode, then it is likely be an external software that is the cause of these scratches.

To open Firefox in Safe Mode, click the Firefox button -> Help -> Restart with Add-ons Disabled.

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Looks to be a skin problem... even if you don't have a custom skin loaded, problems like this can still occur.

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