<script type="text/javascript">    var margintop = $("#header").offset().top       //var marginleft = $("#header_cont").offset().left;   //alert(margintop)   //alert(marginleft)         $(window).scroll(function() {       var scrtop = $(document).scrollTop();       if(scrtop<margintop){        $('#header').css({            position: 'absolute',            top: margintop,            left:'0'          });           return false;      }          $('#header').css({            position: 'absolute',            top: scrtop,            left:'0'          });      });  </script>