if (document.images) { 

var img1on = new Image();
img1on.src = "images/menu/on_home.jpg";
var img1off = new Image();
img1off.src = "images/menu/off_home.jpg";

var img2on = new Image();
img2on.src = "images/menu/on_gaiyo.jpg";
var img2off = new Image();
img2off.src = "images/menu/off_gaiyo.jpg";

var img3on = new Image();
img3on.src = "images/menu/on_gyomu.jpg";
var img3off = new Image();
img3off.src = "images/menu/off_gyomu.jpg";

var img4on = new Image();
img4on.src = "images/menu/on_recruit.jpg";
var img4off = new Image();
img4off.src = "images/menu/off_recruit.jpg";

var img5on = new Image();
img5on.src = "images/menu/on_link.jpg";
var img5off = new Image();
img5off.src = "images/menu/off_link.jpg";

} 

function On(name) { 

if (document.images) { 
document.images[name].src = eval(name + 'on.src'); 
} 

} 

function Off(name) { 

if (document.images) { 
document.images[name].src = eval(name + 'off.src'); 
} 

}