.mydiv {
background-color: #FFCC66;
text-align: center;
line-height: 40px;
font-size: 12px;
font-weight: bold;
z-index:99;
width: 500px;
height: 220px;
left:35%;/*FF IE7*/
top:15%;/*FF IE7*/
margin-left:-150px!important;/*FF IE7 该值为本身宽的一半 */
margin-top:-60px!important;/*FF IE7 该值为本身高的一半*/
margin-top:0px;
position:fixed!important;/*FF IE7*/
position:absolute;/*IE6*/
_top:       expression(eval(document.compatMode &&
            document.compatMode=='CSS1Compat') ?
            documentElement.scrollTop + (document.documentElement.clientHeight-this.offsetHeight)/2 :/*IE6*/
            document.body.scrollTop + (document.body.clientHeight - this.clientHeight)/2);/*IE5 IE5.5*/
}
.bg {
background-color: #666;
width: 100%;
height: 100%;
left:0;
top:0;/*FF IE7*/
filter:alpha(opacity=50);/*IE*/
opacity:0.5;/*FF*/
z-index:1;

position:fixed!important;/*FF IE7*/
position:absolute;/*IE6*/

_top:       expression(eval(document.compatMode &&
            document.compatMode=='CSS1Compat') ?
            documentElement.scrollTop + (document.documentElement.clientHeight-this.offsetHeight)/2 :/*IE6*/
            document.body.scrollTop + (document.body.clientHeight - this.clientHeight)/2);/*IE5 IE5.5*/
}










#Loading {position:absolute;z-index:10;left:10px;top:10px;border:1px #666666 solid;background:#eeeeee;width:10px;height:10px}