First row over my header !!! help me please

Ok this is the problem, my first row is always over my header, so I can't click on my header buttons. If I use obj.setSelectedRows([0]); I lose my header !!!!!
I can't even read my header because both of my datas and my header name are overlaped !

Someone ??

I also noticed that I can't resize my column size :(

Just found the problem !!! I was using an old version of the css file :S 4 hours left for that *&?%*%*% lol Hope this will help you :)