function killRightClick(mButton)
{
     if (document.layers)
     {
          if (mButton.which == 2 || mButton.which == 3)
               return false;
     }
     else
          return false;
}

if (document.layers) // Netscape
{
     document.captureEvents(Event.MOUSEDOWN);
     document.onmousedown = killRightClick;
}
else
     document.oncontextmenu = killRightClick;