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Why do I have 2 red lines at bottom of page stating: < overlay xmlns="http://www. mozilla.org/keymaster/gatekeeper/there.is.only.xul"

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First one line appeared in red at bottom of browser page. A few hours later, a duplicate line in red appeared beneath the first line. This is shortening the browser page and is annoying to look at. I fear it will keep replicating itself and eventually take up the whole page. Help!

First one line appeared in red at bottom of browser page. A few hours later, a duplicate line in red appeared beneath the first line. This is shortening the browser page and is annoying to look at. I fear it will keep replicating itself and eventually take up the whole page. Help!

All Replies (6)

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I should clarify that I am using Nightly. Minkie

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This issue can be caused by an extension that isn't working properly.

Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

  • Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
  • Do NOT click the Reset button on the Safe Mode start window
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Starting in safe mode eliminated the red overlay xmlns line. However, it returned when I restarted Nightly, even after disabling all add-ons. It also returned after switching to the DEFAULT theme. Any suggestions? Thank you.

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If you are familiar with the DOM Inspector then you can try to use this extension to see if that gives a clue of what chrome URI is involved with this screen area.


You can check for problems with preferences.

Delete possible user.js and numbered prefs-##.js files and rename (or delete) the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

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

See "Creating a profile":

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.

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Thank you Cor-el for giving such expert advice. The problem lies in Adblock Plus, and they may be attempting to fix it in their next upgrade. I deleted my original Adblock and downloaded a new version, but the problem persisted. It is eliminated when I disable Adblock totally, but then I have annoying ads. I'll sit tight until the next upgrade and hope that fixes this. Meanwhile, I am most appreciative of the time you took to respond.

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¡Hola!

You could use https://addons.mozilla.org/en-us/firefox/addon/ublock-origin/ in the meantime.

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

¡Gracias!