function $(element) {
  if (typeof (element) == "string")
    element = document.getElementById(element);
  return element;
}

var curImg=1;
function show(id)
{
    $("slide" + curImg).className="";
    curImg = id;   
    $("banner").innerHTML ="<img src='/img/a0"+id+".jpg'>"; 
    $("slide" + curImg).className="slidenow";
}