function control() {
	var pressedKey = String.fromCharCode(event.keyCode).toLowerCase();
	if (event.ctrlKey && (pressedKey == "a" || pressedKey == "u" || pressedKey == "n")) {
		// disable key press porcessing
		event.returnValue = false;
		alert('Funcion Deshabilitada.');
	}
}

function showDown(evt) {
	evt = (evt) ? evt : ((event) ? event : null);
    if (evt) {
    	if ( evt.ctrlKey ) {
        	alert('Funcion Deshabilitada');
            event.preventDefault();
		}
	}
}

// Additional code for NS
if (navigator.appName=="Netscape") {
	document.addEventListener("keypress",showDown,false);
}