Hello,

I think I knew the problem. The browsers have different render behavior.
That's why some of your validation when open DialogBox is not correct in other browser, except IE.
E.g

To open dialog box, I used this code:

function tlbFile_Click(id, toolCommand) 
{
            if (toolCommand.Name == "cmdNew") {
                var dlgBox= ISGetObject("dlgBox");
                dlgBox.SetContentURL("DemoIframePage.aspx");
                dlgBox.Width = 500;
                dlgBox.Height = 300;
                dlgBox.ShowDialog();
//              OpenDialogBox('DemoIframePage.aspx', "", "aaa", "", 500, 300, false);
            }
        }

Normally, you only need to use SetContentURL(" "), when close. However, this method might be not closing its state. In this part, I understand why you get iframe element and set src property.
However, there is a simple way to do it. WebDialogBox already provided this.

e.g
For close dialog box, I used this :

function dlgBox_OnClosed(controlId) 
{
    var dlgBox = ISGetObject(controlId);
    var div = document.getElementById("dvWnd_Global_wnd" + controlId);
    var iframe1 = div.getElementsByTagName("IFRAME");
//    iframe1[0].src = ""; // getRootPath() + "javascript/blank.htm";
    var if1 = document.getElementById("iframe" + controlId);
//    if (if1)
//            if1.style.display = "none";
    dlgBox.Window.GetWindowIFrameElement().src = " ";
}

Regards,
Handy