Would this graphic card work on my motherboard?

My friend gave me his graphic card because he had no use of it and I was wondering if a Radeon 9550XL 256MB would work on my Asus P4S533-VL motherboard.

You didn't say if it was a "e" or "mx" based board, but your video card should be AGP 8x based; and both boards have a AGP 4x slot. So your answer is maybe. They are supposed to clock themselves to match the speed, however; the voltages(0.8 vs 1.5v IIRC) they run at do not have to be compatible. When I worked for ATi we had a lot of issues when AGP 8x came around mainstream.