You can reset the prefs that do that to reverse the action

• Navigate to about:config in your Address Bar
• Press the "I'll be careful, I promise!" button to proceed
• Search for browser.startup.homepage
• Reset the pref by right clicking and selecting Reset
• Restart Firefox

You can delete a possible user.js file and numbered prefs-##.js files and rename (or delete) the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in the current Firefox release. You can get to the profile folder below:

• Help > Troubleshooting Information > Profile Directory > Show Folder

or

• Go to about:support and click Show Folder next to Profile Directory.

Reset was not an option. File says 'locked'

Can you give me a screenshot so I know what you're seeing? Please see How do I create a screenshot of my problem? to create a screenshot
Once you've done this, attach the saved screenshot file to your forum post by clicking the Browse... button below the Post your reply box. This will help us to visualize the problem.

See uploaded image.

How to Remove Safesear.ch Redirect Virus?(Browser Hijacker Removal Guide)
http://forums.anvisoft.com/viewtopic-45-6542-0.html

Right click and reset in about:config search bar = ? This did not work.

In my Tools>Options>General, I cannot edit Home Page

Someone please HELP! 7 different methods to try and get rid of this and ALL HAVE FAILED.

You (or somebody) installed some software or toolbar on your computer/browser and that "free software" introduced this change.

So its not about firefox - its about the software which did this.

http://forums.anvisoft.com/viewtopic-45-6542-0.html tells you (among ohters) :

Step 1. Uninstall unfamiliar and suspicious program from Computer Step 2. Remove unfamiliar extensions and reset your browsers(manually) Optional Troubleshoot--Remove Toolbar/Extensions using Anvi Slim Toolbar Step 3. Clean residing files, invalid registry entries and junk files using Cloud System Booster

In other words - it does not matter how often you reset your browser. As long as the software in question is still active on your computer, that comes back up cause thats the way they finance it - there is no such thin g as a free lunch.

I have tried all you prescribed. Not succeeding. Anybody else?