One of my resources suggests the site you link to is suspicious. I suspect you could have malware. Beware of any spoof messages and warnings that may be generated, and do not use any security fixes that are suddenly and unexpectedly offered.

For more advice and suggestions see this thread: Search bar causes browser to be hijacked

Try installing Adblock Plus for Firefox, and after you select a filter subscription, add fileinxt.com to your filter list. It should fix the bug.