Grid view header not resizing on resizing the window.--

[manojuniverse]

Hi
I have a gridview . I have made the header of gridview fixed by adding a css..as

.Fixedheader
{
position:relative;
top: expression(this.parentNode.offsetParent.scrollTop) ;
}

But now when I resize the window .Gridview header remains at same place at which it was ealier. Header doesnot resize itself..

Can anybody tell me why this is happening and what to do to avoid it..

Manoj Aggarwal