// Netscape 4.x 
if (document.layers){document.write("<link rel='stylesheet' href='res/stile_ns4.css' type='text/css'>");} 
// Explorer e Opera 
else if (document.all){document.write("<link rel='stylesheet' href='res/stile.css' type='text/css'>");}
// Netscape 6.x
else if (document.getElementById){document.write("<link rel='stylesheet' href='res/stile.css' type='text/css'>");}