In this the user cannot switch to the window without closing the existing window. This sort of dialog box is referred to as a modal dialog box. You generate a modal dialog box with showModalDialog().
Syntax: showModalDialog ("Message")
<HTML>
<HEAD>
<SCRIPT LANGUAGE="JAVASCRIPT">
function fnOpenModal(){
window.showModalDialog("test.htm") }... [2]i
</SCRIPT>
</HEAD>
<BODY>
<FORM NAME = IGNOU>
<INPUT TYPE="button" VALUE="Push Me" onclick="fnOpenModal()">
</BODY>
</HTML>