prova così...
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=windows-1250">
<meta name="generator" content="PSPad editor, www.pspad.com">
<title>test</title>
<script>
function cambia(){
var elements=document.getElementsByTagName('*');
alert(elements.length);
for(var n=0;n < elements.length;n++){
if(elements[n].className == 'tizio'){
elements[n].style['color']="#ff0000";
}
}
}
</script>
</head>
<body>
<h2 class="ciccio">ciao mondo</h2>
<h2 class="tizio">cioa mamma</h2>
<h2 class="caio">ciao universo</h2>
<script>cambia()</script>
</body>
</html>