How to generate popup windows in full screen mode making them hard to close?

If you want to trigger a popup window in full screen mode so it is hard to be closed, you can use the fullscreen=yes option when calling the window.open() method. See the following JavaScript code outline:

<a href="javascript:pWindowFullScreenTest();">Click ...
...
<script>
/*
*  Popup Blocker Test - P_WINDOW_FULLSCREEN
*  - Popup Windows Triggered as Full Screen Windows
*
*  A single popup window shows up occupying the entire 
*  screen. JavaScript codes implemented with an open method
*  call.
* 
*  Version of 2007.01.01
*  Download at http://sqa.fyicenter.com/tools/
*  Copyright (C) 2007 FYIcenter.com. All rights reserved.
*/
function pWindowFullScreenTest() {
   fyicenterWin = window.open('',
      '', 'fullscreen=yes');
   fyicenterWin.document.write('<html><body bgcolor="#eee...
   fyicenterWin.document.write('<p><b>P_WINDOW_FULLSCREEN...
   fyicenterWin.document.write(' - Popup Window Triggered...
   fyicenterWin.document.write(' - Developed by FYIcenter...
   fyicenterWin.document.write('<p><img src="/popup_test_f...
   fyicenterWin.document.write('If you see this popup win...
   fyicenterWin.document.write('<p><br/><br/><br/>');
   fyicenterWin.document.write('<b>Press &lt;Alt&gt; + &lt;F
   fyicenterWin.document.write('</body></html>');
   fyicenterWin.document.close();
}
</script>

You can also visit Popup Blocker Test - P_WINDOW_FULLSCREEN page to get the complete source code and to see how it works.