what do i need to disable

Ok, You have been very helpful with my questions so far and I thank you for that. My next task is disable harmful tags/scripts in a full text field. I want to store a bio type field and I am considering allowing html (to allow a myspace type of customization to the page), but I am really new to this so I really don't know what kind of trouble I am asking for. I'm sure that I need to block JavaScript, but are there other things (tags, scripting, etc.) that can be input into my DB that will cause problems either being stored as such or when accessed? Again, thanks for the advice in advance. Don