<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script language="javascript">
function test() {
alert("http://www.selfhtml.org/");
return false;
}
</script>
</head>
<body>
<form action="http://www.selfhtml.org/">
<button type="button" onclick="test()">Test</button>
<input type="submit" />
</form>
</body>
</html>
Wichtig ist die Angabe von type="button", da der default Wert submit ist. (Danke nochmal an: dedlfix)