function setPng24(obj) { 
  obj.width=obj.height=1; 
  obj.className=obj.className.replace(/\bpng24\b/i,''); 
  obj.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='"+ obj.src +"',sizingMethod='image')";
  obj.src='';  
  return ''; 
}

function change(){
	number = Math.floor(Math.random()*2)+1;
	document.getElementById('r_bg').className="back"+number;
}