Those settings are for personal use and they are there for you to decide what you prefer for your browsing enjoyment.
Some of the settings are to do with security and privacy, and you would need to examine these, and use utilities like Google to find out more.
It's really very difficult for us to tell you what settings you should look at, even more change.
i use firefox,but for the last 3 days i have been trying out opera and beleive it or not i like it alot.it seems faster than firefox 3 on my pc.i might even just make it my new browser of choice.i just wanted to know if im suppose to leave it just like it is after downloading it,i mean, do i leave it on its default settings or what?case when i go to preferences it has alot of settings an its hard to understand.can anyone help me out on this an help me set up opera? thanks i really appreciate it!