Thanks for all answers.
Yes I heard of antivirus proggies for linux, AVG has one. But I don't feel like setting one up. Do you guys use one?
Right now, I have used Firebid as my main browser, I do know how to keep this under control here, < internet history, cookies and else >
I was curious about hard disk space, like one month from now, I could erase tmp folders or stuff Linux has been caching that I don't need so I can make a little more room to my drive.
About running as *su*, I would only do this if I need special privileges to run a command, though I don't browse the web as root, just in case.