function over(id) {
 document.getElementById(id).src = "images/top/" + id + ".png";
}

function out(id) {
 sid = id.substring(1);
 document.getElementById(id).src = "images/top/" + sid + ".png";
}

function n_over(id) {
 document.getElementById(id).src = "images/nav/o" + id + ".png";
}

function n_out(id) {
 document.getElementById(id).src = "images/nav/n" + id + ".png";
}

/*function nav_over(id) {
 document.getElementById(id).src = "images/" + id + "_big.gif";
}

function nav_out(id) {
 document.getElementById(id).src = "images/" + id + ".gif";
}*/