Floating Headers in ASP.NET DataGrid/Gridview in popup

Question

How Can i Achieve Multi -Browser Support for Floating Headers in Gridview/Datagrid in  a popup window?

My CSS: 

 .gridheading1 

{

 position:absolute

top: expression(this.offset.scrolltop-1 )

} 

 

 

1) This  is disturbing css of my gridvew as the gridlines appear to be broken in middle or end.

2) While viewing in chrome or FireFox,  headers appear to be slightly misaligned with item in gridview.

how can i solve the issue of perfectly aligning the gridview headers with items or rows of gridview?