Disabling window onbeforeunload function in a link
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i have a site using  window onbeforeunload function but popup on click is not working because of it. how can i integrate the code 

    window.onbeforeunload="null";
in the popup code below

    <script type='text/javascript'>
        
        	function ouvre(fichier) {
        	   	  ff=window.open(fichier,"popup","width=600px,height=300px,left=50%,top=50%") 	 </script>

     <a href="#" onClick="ouvre('http://www.facebook.com/sharer.php?u=http://google.com/');window.onbeforeunload="null";return false"><img src="http://i.imgur.com/GnqwI.jpg" width="500" height="145" border="0"></a>


