[javascript] Adding an onclick event to a div element

I saw a few similar topics which did help but I have specific problem and didn't manage to solve it alone so if anyone can help out I would appreciate it

I want to add onclick event to a div element.

HTML:

<div id="thumb0" class="thumbs" onclick="klikaj('rad1')"></div>

JavaScript:

function klikaj(i)
{
    document.getElementById(i).style.visibility='visible';
}

Wanted result: div with id="rad1" (which is hidden) turns visible, when clicked on div with id="thumb0".

This works when I add it to a button element but don't know how it goes with div elements.

I'm not sure what the problem is; running the below works as expected:

<div id="thumb0" class="thumbs" onclick="klikaj('rad1')">knock knock</div>
?<div id="rad1" style="visibility: hidden">hello world</div>????????????????????????????????
<script>
function klikaj(i) {
    document.getElementById(i).style.visibility='visible';
}
</script>

See also: http://jsfiddle.net/5tD4P/