Code
function cancelBubbling(evt){
if(!evt) var evt = window.event;
evt.cancelBubble = true; //IE style
if (evt.stopPropagation) evt.stopPropagation();// MOZ style
}
function showRightClickMenu(e){
dbgDump("rClick!!!");// show something in the debug window
cancelBubling(e);
}
/*-------------------------------------------------------*/
<body oncontextmenu='showRightClickMenu(event);return false;'>