How to write html code dynamically using JavaScript?

<script type="text/javascript" >

function contactform() {

var contactdata="Name:<input type='text' name='name'><br>Message:<br><textarea rows='3' cols='10'></textarea> <br><input type='submit' value='Submit'>";

document.getElementById('display').innerHTML=contactdata;

}

</script>
<form name="contact">

<input type="button" value="contact" onclick="contactform()">

<div id="display"></div>

</form>