var key = new Array();  
key['s'] = "http://philippe.landes.free.fr/new/sommaire.php";
key['x'] = "http://philippe.landes.free.fr/new/index.htm";

function getKey(keyStroke) {
isNetscape=(document.layers);
eventChooser = (isNetscape) ? keyStroke.which : event.keyCode;
which = String.fromCharCode(eventChooser).toLowerCase();
for (var i in key) if (which == i) window.location = key[i];
}
document.onkeypress = getKey;