function OpenCenterPopUp(){     
    var Left=window.screen.width/2-175; 
    var Top=window.screen.height/2-175; 
    var Configuration="'toolbar=no, menubar=no, location=no, directories=no, status=no, resizeable=no, width=520, height=300, left=" + Left + ", top=" + Top; 
    window.open('popup.html','Accès',Configuration); 
}