function popwin(img,w,h){
var x1 = screen.width;
var y1 = screen.height;
var top = parseInt((y1 - h)/2);
var left = parseInt((x1 - w)/2);
window.open(img,'show','width='+w+',height='+h+',resizable=no,scrollbars=yes,status=no,top='+top+',left='+left);
return false;
}