• empty your cache.

• Search for any added text to your starts-shortcut like that url.

• Look for a user.js -file in your Firefox profil (On Windows its "

%appdata%/roaming/mozilla/firefox/profiles/ ????default/  where ???? being some random letters/numbers" ) Is that address same on a mac? 

If you find user.js and haven't created it yourself delete or rename it. Otherwise scan it for barisderin.com and erase or alter that line.

• start FF in safe-mode

• open config ( about:config), search for browser.startup.homepage, set that to your homepage OR about:blank

• You can also search for barisderin.com and hopefully you don't find it

You may have ad / mal-ware. http://www.clamxav.com/ free malware scanner for Mac OS X https://discussions.apple.com/docs/DOC-3291

Adblock Plus {web link} Blocks annoying video ads on YouTube, Facebook ads, banners and much more. Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).

BlockSite {web link} BlockSite is an extension, which automagically blocks websites of your choice. Additionally, this extension will disable all hyperlinks to these websites, by just displaying the link text without the clicking functionality.

http://barisderin.com/?p=1117 is the home-site of You Tube High Definition a Baris Derin add-on. I use it, but every time I'v updated, I empty my cache before I do anything else. He wants a contribution and this is his way of getting attention. But I must say after the last update there wasn't any http://barisderin.com/?p=1117 -page