Opera / FireFox / IE - Cookie Handling

Does anyone know the differences between these 3 browsers when it comes to how they actual handle cookies, for the past couple of months ive been having issues with both IE and FireFox storing cookies on a couple of our in-house systems yet today upon trying the latest release of Opera, all of these issues seem to have vanished.

Im guessing it has to be something specific to the Opera browser and the method it utilizes when it comes to handling cookies.

Regards,

Lee