This work for me
Demo: jsfiddle
$(function()
{
Fixed_Header();
});
function Fixed_Header()
{
$('.User_Table thead').css({'position': 'absolute'});
$('.User_Table tbody tr:eq("2") td').each(function(index,e){
$('.User_Table thead tr th:eq("'+index+'")').css({'width' : $(this).outerWidth() +"px" });
});
var Header_Height = $('.User_Table thead').outerHeight();
$('.User_Table thead').css({'margin-top' : "-"+Header_Height+"px"});
$('.User_Table').css({'margin-top' : Header_Height+"px"});
}