.popupdiv {
    position: absolute;
    z-index: 100;
    width: 1000px;
    height: 600px;
    left: 50%; /*FF IE7*/
    top: 50%; /*FF IE7*/
    margin-left: -500px !important; /*FF IE7 该值为本身宽的一半 */
    margin-top: -300px !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*/
}

.popupbg {
    background-color: #666;
    z-index: 99;
    width: 100%;
    height: 100%;
    left: 0;
    top: 0; /*FF IE7*/
    display: none;
    width: 100%;
    height: 100%;
    opacity: 0.5;
    filter: alpha(opacity=50); /*IE*/
    opacity: 0.5; /*FF*/
    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*/
}