How can I delete or modify preference name?

can u be more specifiQ?

I think you can't. You just make some changes like to customize your browser we add new addons, skins and configure it for increase your browsing speed. I know this post is so much old but it helps other who wanted to know or use firefox

Oh, by the way, I've given up hope of fixing it.

Some day I am going to un-install and re-install Firefox.