Here is the procedure to remove http://search.fbdownloader.com and http://native-search.com, in order to reinstall the desired homepage. http://search.fbdownloader.com is a search engine installed by parasites programs.
Download AdwCleaner (by Xplode), run it and click on Remove. When the scan is completed, you may be asked to restart the computer. A report will then be generated.
Malwarebytes' Anti-Malware (MBAM) is an effective cleaning tool thant can achieve removal of files left behind by AdwCleaner. After installing, do an update of the malware database, then launch a full scan. Once the analysis is done, click on "Show results". Select all infected items and click on "Remove Selected". If prompted to do so, reboot the computer.
Clean your browsers - Uninstall parasite extensions
Firefox: Tools > Add-ons > Extension tab.
Google Chrome: Click on the Settings menu> Tools / Extensions
Remove the parasites extensions
You should be very careful when you're installing free softwares, as many of them are bundled with potentially unwanted programs.