if (document.images) { 

var img1on = new Image();
img1on.src = "images/btn_products2_on.gif"; 
var img1off = new Image();
img1off.src = "images/btn_products2.gif";

var img2on = new Image();
img2on.src = "images/btn_products_on.gif"; 
var img2off = new Image();
img2off.src = "images/btn_products.gif";

var img3on = new Image();
img3on.src = "images/btn_company_on.gif"; 
var img3off = new Image();
img3off.src = "images/btn_company.gif";

var img4on = new Image();
img4on.src = "images/btn_contact_on.gif"; 
var img4off = new Image();
img4off.src = "images/btn_contact.gif";
} 


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'); 
} 

}