hello, can you try to replicate this behaviour when you launch firefox in safe mode once? if not, maybe an addon is interfering here...

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Please provide a screenshot of that grey bar and that code.

https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-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 is the screenshot of the problem.

Looks like a fault with Adblock Plus. See the Adblock Plus forum.

http://adblockplus.org/forum/

Yes. That is likely a problem with a broken extension as posted above.

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

• Do NOT click the Reset button on the Safe Mode start window.

If it works in Safe Mode and in normal mode with all extensions (Firefox/Tools > Add-ons > Extensions) disabled then try to find which extension is causing it by enabling one extension at a time until the problem reappears.

Close and restart Firefox after each change via "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: Firefox > Quit Firefox; Linux: Firefox/File > Quit)

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

I followed the safe mode instructions above. No one add-on seemed to trigger the strange bar. However, systematically disabling all the add-ons and testing them one-by-one, and then restarting them one at a time seems to have cleared the problem. I don't know why. I seem to be running both Adblock Plus and Trueblock ... would that be a problem?

Thanks for the help.

I've seen a report that Trueblock can cause this issue.