YAHOO.util.Event.onDOMReady(
    function(){
        var Ev = YAHOO.util.Event;
        Ev.on(document.body, 'contextmenu', function(e){Ev.stopEvent(e);});
        Ev.on(document.body, 'copy', function(e){Ev.stopEvent(e);});
        Ev.on(document.body, 'selectstart', function(e){Ev.stopEvent(e);});
    }
);