This does not seem normal, but have you tried Diagnose Firefox issues using Troubleshoot Mode If not luck please try a virus scan: Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

Sounds like the problem several users have reported with "SmarterMail".

As a short term workaround, try double-clicking the title bar of the self-shrinking window to maximize it. The script that resizes the window should not run when the window is maximized.

Apparently a fix is available from the vendor, but when your mailbox gets the fix will depend on your mail host. Note that after it becomes available, you may need to clear Firefox's cache to get the fixed files.

See: https://support.mozilla.org/questions/1013240

Thanks for the replies.

I have already run a virus scan - I have Norton Internet Security. I've also tried maximising the window - it just progressively shrinks down again.

For the moment, I'm getting round the problem by using Chrome. The fix mentioned in the other post seems to be the answer, but I'll need to get on to my hosting company to implement it.

Willl let you know if it works.

Hi Stevep17, thank you for testing that, and sorry to hear it didn't work.

You can block website scripts from resizing windows. It's a bit of a sledgehammer, but another user who has this problem indicated that it does stop the SmarterMail script from rolling up the window.

Here's how:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste dom and pause while the list is filtered

(3) Double-click the dom.disable_window_move_resize preference to switch it from false to true.

The problem has now been resolved. My hosting company upgraded to Smartermail Enterprise 12.3 and it all works normally now.

Thanks for all your help.