兼容ie，firefox window.showModalDialog

计算Dialog居中位置。

function CalcShowModalDialogLocation(dialogWidth, dialogHeight) {
    var iWidth = dialogWidth;
    var iHeight = dialogHeight;
    var iTop = (window.screen.availHeight - 20 - iHeight) / 2;
    var iLeft = (window.screen.availWidth - 10 - iWidth) / 2;
    return 'dialogWidth:' + iWidth + 'px;dialogHeight:' + iHeight + 'px;dialogTop: ' + iTop + 'px; dialogLeft: ' + iLeft + 'px;center:yes;scroll:no;status:no;resizable:0;location:no';
}

调用Dialog位置方法。 

 var DialogLocation = CalcShowModalDialogLocation(500, 260);
                var result = window.showModalDialog("URL", window, DialogLocation);