Creating true modal dialogs in browsers other than Internet Explorer is not easy - showModalDialog is a MSIE thing. And then there are other issues
a. Lack of control over the dialog UI
b. Cumbersome access to objects in the document from which the modal dialog was opened
c. Modals blocked by user browser settings or a firewall
All of these problems can b e avoided by simply creating a simulated modal dialog using the power of CSS. Here is a tutorial explaining how