It's possible that you are having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

Whenever you have a problem with Firefox, whatever it is, you should make sure it's not caused by one (or more than one) of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode (don't forget to select Disable all add-ons when you start safe mode). If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and themes and this one for plugins.

If you need support for one of your add-ons, you'll have to contact its author.

If the problem does not disappear when all add-ons are disabled, please tell me, so we can work from there. Please have no fear of following my instructions to the line, as all can be easily undone.

Rokkan, is it possible you are using these new Personas? http://www.getpersonas.com/en-US/#plus

A screenshot would be helpful, if you could post one.

i have this problem too i was on a site then my java popped up saying something was trying to access it then now i have this as a background image https://ibank.barclays.co.uk/s/glo/img/bg/eagle.jpg its as if its been hacked any help will be appreciated

Possibly you need to update JAVA plugin.

Tools -> Options, "Manage Add-ons..." , Plugins, "Find Updates". See if you are up to date.

Or use chrome instead.

I suspect a trojan here. I have the same issue and when I look at my page source it is full of Barclays bank css styles. I have never visited their site.

I also got a warning earlier today from my antivirus about a trojan this was `cleaned` but I still think there is a problem. I also got a warning that my firewall was switched off.

I am now doing a full virus scan and will report back (its going to take ages)

This background image is also in IE.

Arthur.

I'm also having this problem, it is most definitely some sort of phising attempt. I have run a full Malwarebytes scan but that's not been enough. Will now try Avira AntiVirand AVG Anti-Virus If anyone knows how to remove this trojan please get in touch.

Damn, forgot all about this... Didn't find anything disabling add-ons, running AV or anything. In the end I backed up all my data and did a restore to factory settings, that seems to have kicked it. Time consuming and annoying I know, but it worked.

yes its a trojan - combofix will get rid of this. look for the following files - they seem to be the core of the issue...

C:\iTunesinst.exe folder c:\users\<UserName>\g2mdlhlpx.exe

I don't have either of those two folders, and so I am having a hard time finding out if I have that exe file or not.

I have tried a full scan with these four antivirus/antimalware programs but I've not been able to find this trojan and remove it. Avira Antivir AVG Anti-Virus Malwarebytes Anti-Malware Windows Defender

This is just so extremely frustrating, what can I do?

Microsoft Security Essentials managed to find and erase the trojan.

Just and update.

I ran Spybot and that seems to have done the trick.