html,body {height:100%; margin:0px; font-size:12px;}

.mydiv {
text-align: center;
font-size: 12px;
z-index:9999;
/*/width: 500px;/*/
/*/height: 125px;/*/
left:50%;/*FF IE7*/
top:50%;/*FF IE7*/

margin-left:-160px!important;/*FF IE7 该值为本身宽的一半 */
margin-top:-100px!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*/

}



.mydiv1 {
text-align: center;
font-size: 12px;
z-index:9998;
/*/width: 500px;/*/
/*/height: 125px;/*/
left:50%;/*FF IE7*/
top:50%;/*FF IE7*/

margin-left:-160px!important;/*FF IE7 该值为本身宽的一半 */
margin-top:500px!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*/

}