onClick message dissapears

I used some javascript to make a "thank you for subscribing" message appear
after someone clicks a submit button to subscribe to an email list. The problem
is, it stays for about 2 seconds, then goes away. Does anyone know how to make
it stay after the button is clicked?
here is the code I used:

<script type="text/javascript">
function changeText(){
document.getElementById('emaillist').innerHTML = 'Thank you for subscribing';
}
</script>
<input type=submit value="Submit" onclick='changeText()'/>
</p><h2><b id='emaillist'>[/b] </h2>


Thanks!