var moz = false;

function click(e) {
  if (document.all) {
    if (event.button == 2 || event.button ==3) {
      return false;
    }
  }
  if (document.layers || moz) {
    if (e.which == 2 || e.which == 3) {
      return false;
    }
  }
}

if (navigator.appName == "Mozilla" || (navigator.appName == "Netscape" && navigator.appVersion.indexOf("4.") == -1)) {
  moz = true;
}
if (moz) document.addEventListener("mousedown",click,true)
else if(navigator.appName == "Netscape" && navigator.appVersion.indexOf("4.") != -1) document.captureEvents(Event.MOUSEDOWN)

if (!moz) document.onmousedown = click