var temp = new Image();
var loc;
var gotit;

function checkit(){
  if ((navigator.appName=="Microsoft Internet Explorer") && (parseInt(navigator.appVersion) >= 4)) return; 
  else alert("To play, you need MSIE 4 or greater");
} 

function exch(){
  if ((event.button == 1) && (event.srcElement.className == "drag")) {
    if (gotit == 1) {
      gotit = 0 ;
      document.images[loc].src = document.images[event.srcElement.name].src ;
      document.images[event.srcElement.name].src = temp.src ;
      } 
  else {
    gotit = 1 ;
    loc = event.srcElement.name ;
    temp.src = document.images[loc].src ;
    }
  }
}




function exch(e){
  if (!e)
    e = window.event; 
    sorgente = (e.target) ? e.target: e.srcElement;

  if ((e.button <= 1 ) && (sorgente.className == "drag")) {
    if (gotit == 1) {
      gotit = 0 ;
      document.images[loc].src = document.images[sorgente.name].src ;
      document.images[sorgente.name].src = temp.src ;
      }
    else {
      gotit = 1 ;
      loc = sorgente.name ;
      //alert(loc);
      temp.src = document.images[loc].src ;
      }
    }
}


document.onmousedown=exch