showDiv($("#pop"));function showDiv(obj){ $(obj).show(); center(obj); $(window).scroll(function(){  center(obj); }); $(window).resize(function(){  center(obj); }); }function center(obj){ var windowWidth = document.documentElement.clientWidth;    var windowHeight = document.documentElement.clientHeight;    var popupHeight = $(obj).height();    var popupWidth = $(obj).width();     $(obj).css({     "position": "absolute",     "top": (windowHeight-popupHeight)/2+$(document).scrollTop(),     "left": (windowWidth-popupWidth)/2    });  }