Fixed Header in Gridview

Question

Hi,

   In my gridview, i need to fix the header while scrolling the grid.

I tried .css

.HeaderFreez 

{ 	

   position:relative ; 	

   top:expression(this.offsetParent.scrollTop); 	

   z-index: 10; 

}

but the top style doesn't work. Is there any way to fix my header????

Plz help me if u know???? :)