<!---- start:
var popUpWin;   // use for all windows
function showPopUp(content)
{

if ((popUpWin != null) && (!popUpWin.closed)) {
    popUpWin.close(); 
}
popUpWin = window.open(content,'fb','scrollbars=yes,resizable=yes,height=550,width=750');
}
<!----end---->