I followed the instructions here
http://support.microsoft.com/kb/825532
After that when I preview my page, I can't see the hitcounter. I learned that it may be related to permissions of the site but I couldn't find how to do it.
Is it realy related to permissions ? If so what should I do to ? And any external solution (except this one: http://hitcounter.codeplex.com/) would help, the one in pharanthesis, I couldn't make it work.