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I have this problem with Firefox when using Facebook that when I want to close the tab containing facebook it doesn't let me. I mean no matter how many times I middle-click on the tab or use the close button, the tab won't be closed.
I guess the problem is with some javascript code on the page because if I wait long enough it alerts that some script on the page is not responding although the page itself IS generally responsive and ok.
I wonder if anyone has ever faced such a problem? I use Firefox 12 and the problem is consistent across Linux (Ubuntu 12.04) and Windows 7.

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What exactly is the URI given in the alert? Some Facebook URI? Or maybe some chrome URI belonging to an extension, you have installed? – Gurken Papst May 7 '12 at 21:55
up vote 0 down vote accepted

I created this userscript to disable the onbeforeunload handlers in facebook. Of course, you need Greasemonkey.

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It is actually due to Facebook running a number of scripts on Tab Close.

As mentioned above it is the OnUnload event

I wrote a little GreaseMonkey script for it since it was greatly annoying

Good luck


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Under Windows try running Firefox in safe mode > Start > Run > firefox /safe and see how it behaves..Start eliminating unwanted addons and check behaviour each time...

Another thing to consider is checking and updating addons etc... Visit qualys's browsercheck online service

Also, try to clear your browser's cache/temp files etc.

Finally, if everything else fails, i would revert to a previous version i.e. 11 and see how things turn out...

visit for older versions of Firefox and software...

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Warning: Reverting to an outdated version is dangerous, because older versions usually contain known security vulnerabilities. Outdated versions should only be used for testing purposes on trusted sites. If it should turn out, that one of your extensions does not behave well with version 12, you might want to give Firefox ESR a try: – Gurken Papst May 7 '12 at 21:43
@GurkenPapst: thanks! you are 100% right on that...what i forgot to say whan to upgrade to the newest version afterwards...usually fresh new versions fall back on some plugins' i just use a version back... – DeemV May 8 '12 at 16:57

Open task manager (in Windows 7, CTRL-ALT-DEL) and go to the processes tab. Find the process named "plugin-container.exe" with the description "Plugin Container for Firefox" and end that process and then see if Firefox begins functioning properly.

I've found this is a relatively reliable way to get the good ol' FF up and running again without having to start everything over. You may need to reload tabs open to video sites and other plugin-intensive pages, but otherwise everything should be OK.

It's also a clue that the issue is with one (or more) of your plugins. You should at least check to make sure you've got a current version of Java and Flash installed for FF. Use this site to check your plugins up-to-date status:

Regarding Linux. I'm not sure if they use the same executable name for the plugin container, and I have not checked this fix there.

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Same here, Firefox 12 under Windows and when trying to close the Facebook tab, it hangs for quite some time, unless I close and reopen Firefox entirely.

My suspicion is not on any Firefox extensions, but on an unfortunate combination of ban effects:

  • For one, my internet connection is slow. Sometimes requests take ages to either start or time out.

  • Secondly I suspect Facebook using an AJAX request in the OnUnload event, which basically delays the page close until the script decided whether closing is allowed or not.

The problem is, web designers these days can no longer imagine that people will notice these requests because they take so long on their connection.

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Here same problem with slow network connection. – Ali Shakiba May 19 '12 at 17:24

There is a pretty much complete guide to track down and solve problems you can experience in Firefox:

Without knowing more details of your configuration (ie. used extensions), there is probably no other reliable way to get rid your of problem. I would expect an extension as the most likely cause, but this might lead you into the wrong direction. So better just follow the guide step by step.

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