m1_off = new Image();
m1_off.src = "i/sitemap_ico.gif";
m1_ovr = new Image();
m1_ovr.src = "i/sitemap_ico_a.gif";

m2_off = new Image();
m2_off.src = "i/mail_ico.gif";
m2_ovr = new Image();
m2_ovr.src = "i/mail_ico_a.gif";

m3_off = new Image();
m3_off.src = "i/home_ico.gif";
m3_ovr = new Image();
m3_ovr.src = "i/home_ico_a.gif";

function ovr(img)
{
var imgovr = eval(img + "_ovr.src");
document.images[img].src = imgovr;
}

function off(img)
{
var imgoff = eval(img + "_off.src");
document.images[img].src = imgoff;
}