Any idea what the extension was? Often when you remove an extension, it leaves behind some footprints in your preferences. Could you look here:

(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 exten and pause while the list is filtered

(3) If you look at the matches, a common pattern is extension.extensionname.setting_name

Does that help identify what might be missing?

It's hard to understand why removing an extension would break your ability to connect to the internet. Did you uninstall anything outside Firefox?

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

I rebooted my PC and Firefox is working! the problem now is when I open a new tab the following message appears:

File not found Firefox can't find the file at chrome://quick_start/content/index.html. Check the file name for capitalization or other typing errors. Check to see if the file was moved, renamed or deleted.

I suppose that is because of the extension I deleted. How can I get it back?

Thanks for the help!

Quick Start, hmm, did you really like it or would you be happy with the built-in new tab page?

Here's how you can change your new tab page:

(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 newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter your preferred page:

• Page thumbnails (default) => about:newtab
• Blank tab => about:blank
• Built-in Firefox home page => about:home
• Any other page => full URL to the page

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

Fixed! Thank you! :)

You can open the about:config page via the location/address bar and search for prefs that refer to quick_start. You can reset user set (bold) prefs via the right-click context menu to the default value.