shown=''
function windowopen(url, w, h){
	if( shown=='' || shown.closed) {
		shown=window.open(url, 'windowopen', 'toolbar=0,scrollbars=0,location=0,directories=0,status=0,menubar=0,resizable=0,width='+w+',height='+h);
	} else {
		shown.close();
		shown=window.open(url, 'windowopen', 'toolbar=0,scrollbars=0,location=0,directories=0,status=0,menubar=0,resizable=0,width='+w+',height='+h);
	} 
}