daveVk - 10:29 pm on Jan 2, 2013 (gmt 0)

I guess only one click is valid, so maybe

<script type="text/javascript">
function showCoupon(el) {
el.style.display == "none"; // hide link
document.getElementById('couponcode').style.display = ''; // show coupon
document.getElementById('couponImage').src = 'http://www.example.com/'; // cookie stuff
return false; // do not follow link
}
</script>

HTML code

<a href="#" onClick="showCoupon(this)">Click here to get the coupon code</a>
<div id="couponcode" style="display:none;"><strong>MYCOUPON</strong></div>
<img id="couponImage" src="/dummy.gif" width="1" height="1"/> // use a valid image url