Canceling the Closing of a Modal Dialog Box Causes Box to Close Anyway

Setting event.returnValue inside an onbeforeunload event for a window causes Internet Explorer to prompt you whether you want to close the current window. In a modal dialog box, if you instruct Internet Explorer to keep the window open, the window may close anyway. This issue affects windows that are created with the window.showModalDialog and window.showModelessDialog functions.

To resolve this problem, obtain the latest service pack for Internet Explorer version 5.01. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Internet Explorer version 5.01 Service Pack 2.