DIALOG.XUL

<?xml version="1.0"?>
<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>

<dialog 
   onload="init();"
   xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"

   <script src="dialog.js"/>
   
   buttons="accept,cancel"
   buttonlabelcancel="Cancel" buttonlabelaccept="OK"
   ondialogaccept="{alert('OK');}" ondialogcancel="{alert('Cancel');}">
  
  <hbox>
    Notify me when :   
  </hbox>
  
  <checkbox label="goes on-line" checked="{true | *false}"/>
  <checkbox label="goes off-line" checked="{true | *false}"/>

</dialog>