I'm not shure if this has been discudssed before, but can someone explain me what's the 95% rule and why people hate it do much ? (Or give me a link to a previous discussion .. I can't find none)

Hmmm... you must be using the wrong search term! There've been many, many discussions of it here. I just searched for "95th" and got a page or so of results; I'd recommend you start with this one:

http://www.webhostingtalk.com/showthread.php?threadid=1808

Thank you jay .. no need to continue this thread, that shure explains it :)