var cur=1;
function doSelect(num)
{  document.getElementById('ch'+cur).className="";
  document.getElementById('ch'+num).className="selected";
  if (navigator.appName == "Microsoft Internet Explorer")
  {
   	document.getElementById('img_big').style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + imgs['img'+num] + "', sizingMethod='scale')";
  }
  else
  {  	document.getElementById('img_big').src=img['img'+num].src;  }
  cur=num;}