<script type="text/javascript">
    if(document.getElementById('number1').checked) {

             <h1>Hello member</h1>}
       </script>

<script type="text/javascript">
if(document.getElementById('number1').checked) {
    document.write("<h1>Hello member</h1>");
}
</script>

<script type="text/javascript">
window.onload = function() {
    if(document.getElementById('number1').checked) {
        var h1 = document.createElement("h1");
        h1.appendChild(document.createTextNode("Hello member"));
        document.getElementById("XXX").appendChild(h1);
    }
}
</script>

<script type="text/javascript">
if(document.getElementById('number1').checked) {
document.write("<h1>Hello" +
"member</h1>");
}
</script>

<div id="demo></div>

   <script type="text/javascript">
        if(document.getElementById('number1').checked) {
             var demo = document.getElementById("demo");
             demo.innerHtml='<h1>Hello member</h1>';
        } else {
             demo.innerHtml='';
        }
    </script>