var Mot = "plan",
    Adresse = "plan_du_site.htm",
    Lettre = 0;
function getKey(keyStroke) {
var isNetscape=(document.layers);
var eventChooser = (isNetscape) ? keyStroke.which : event.keyCode;
var which = String.fromCharCode(eventChooser).toLowerCase();
if (which == Mot.charAt(Lettre)) {
Lettre++;
if (Lettre == Mot.length) window.location = Adresse;
}
else Lettre = 0;
}
document.onkeypress = getKey;