function clickIE() {
  if (document.all) {
    return false;
  }
} 
function clickNS(e) {
  if (document.layers||(document.getElementById&&!document.all)) { 
    if (e.which==2||e.which==3) {
      return false;
    }
  }
} 
if (document.layers) {
  document.captureEvents(Event.MOUSEDOWN);
  document.onmousedown=clickNS;
} 
else{
  document.onmouseup=clickNS;
  document.oncontextmenu=clickIE;
} 
document.oncontextmenu=new Function("return false")