function show(el) {

	if (el == "viano") {
		document.getElementById('istruzioni').style.display = "none";
		document.getElementById('classeE').style.display = "none";
		document.getElementById('viano').style.display = "block";
	}

	if (el == "classeE") {
		document.getElementById('istruzioni').style.display = "none";
		document.getElementById('classeE').style.display = "block";
		document.getElementById('viano').style.display = "none";
	}

}


function center_main() {
 	winH = typeof( window.innerHeight) !== "undefined" ?
	window.innerHeight :
	document.documentElement.clientHeight;
	mt = (winH - 420 ) / 2 - 10;
	if (mt < 0) mt = 0;
	document.getElementById('container').style.marginTop = mt + "px";
}