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
• TDSSKiller - AntiRootkit Utility

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!

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Hello,

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• You can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

Thank you.

Thank you iamjayakumars for responding to my problem. Firstly, I have Microsoft Security Essentials as my antivirus and it didn't find any malicious thing in my computer. Secondly, I tried opening my Firefox in safe mode with my addons disabled but it didn't help. I still have that problem. I am attaching a snapshot of the page which opens when i click on new tab button.

here is how you restore or change your new tab. Thanks to jscher2000 in another post.

  Quoting 
      "Here is how you can reset what the tab does. If this setting does not stick, one of your add-ons might be overriding it.

(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 filter box, type or paste newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter the desired value:

(i) Page thumbnails (default)

about:newtab

(ii) Blank tab

about:blank

(iii) Built-in Firefox home page

about:home

(iv) Any other page

full URL to the page

Press Ctrl+t to open a new tab and verify that it worked."

I hope this helped you it sure helped me and Thanks jscher2000, you saved me from pulling my hair out.