Collabsable table/div without javascript

I'm trying to get a collabsable table or div for use in forum signatures.

<div>
    <CENTER><div class="pre-spoiler">
    <span style="float: left; padding-top: 2px;"></span> <input value="Show F.A.Q." style="margin: 0px; padding: 0px; width: 75px; font-size: 10px;" onclick="if (this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display != '') { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = '';this.innerText = ''; this.value = 'Hide F.A.Q.'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = 'none'; this.value = 'Show F.A.Q.';}" type="button">
    </div>

    <div>
        <div class="spoiler" style="display: none;"><br>

test
</div>
</div>

PHP:

Because it's a forum signature it cannot use javascript.
This code works in a plain html document, but for some reason it doesn't on the forum.
The button appears, but when I click it nothing happens. Also the button text doesnt change to 'hide FAQ'. It just gets pressed thats all.

Any suggestions, or other code snippets I could use?
Thanks very much