Make the contents of the entire form erasable with a button!

<input type="text" id="username"/>
<input type="password" id="password"/>
<input type="button" id="btn" value="Clear"/>
<script type="text/javascript">
    document.getElementById("btn").onclick = function () {

        document.getElementById("username").value = "";
        document.getElementById("password").value = "";
    }
</script>