var zoomwin;

function prevwin(pic) {
	if(zoomwin) {
		zoomwin.close();
		zoomwin = window.open("zoom.php?pic="+pic,"zoomwin","width=640,height=502,address=no");
		zoomwin.focus();
	} else {
		zoomwin = window.open("zoom.php?pic="+pic,"zoomwin","width=640,height=502,address=no");
		zoomwin.focus();
	}
}