//背景css:
#fullbg{
position:absolute;
cursor:pointer;
background-color: #000000;
display: none;
z-index: 100;
left: 0px;
top: 0px;
filter: Alpha(Opacity=50);
-moz-opacity: 0.5;
opacity: 0.5;
}
//弹出背景html:
<div id="fullbg"></div>
//弹出框div的id:
tishi_info
//弹出js函数:
function show_tishi()
{
var bH = $(document).height();
var bW = $(document).width();
$("#fullbg").css({ width: bW, height: bH, display: "block" });
var x=$(window).width()/2;
var y=$(window).height()/2;
var div_w=$("#tishi_info").width()/2;
var div_h=$("#tishi_info").height()/2;
var stop=document.documentElement.scrollTop;
var sleft=$("tishi_info").scrollLeft();
var left=x-div_w+sleft+"px";
var top=y-div_h+stop+"px";
$("#tishi_info").css({"position": "absolute",left:left,top:top});
$("#tishi_info").show('block');
}