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

   if ( document.layers ) {
      if ( e.which == 3 ) {
         oncontextmenu = 'return false';
      }
   }
}

if ( document.layers ) {
   document.captureEvents(Event.MOUSEDOWN);
}

document.onmousedown = click;
document.oncontextmenu = new Function("return false;");