[Code Monkey]

I've played with the code a bit. I think this looks nicer than having an empty box. Plus it has less divs.

    <div>
        <input type="button" value="Show Spoiler" style="width:80px;font-size:10px;margin:0px;padding:0px;" onclick="if (this.parentNode.parentNode.getElementsByTagName('div')[1].style.display != '') { this.parentNode.parentNode.getElementsByTagName('div')[1].style.display = ''; this.parentNode.parentNode.getElementsByTagName('div')[2].style.display = 'none'; this.innerText = ''; this.value = 'Hide Spoiler'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].style.display = 'none'; this.parentNode.parentNode.getElementsByTagName('div')[2].style.display = ''; this.innerText = ''; this.value = 'Show Spoiler'; }" />

        <div id="spoiler" style="display: none;margin: 0px; padding: 6px; border: 1px inset;width:560px">
           {param}
        </div>

        <div style="display:block; font-style:italic;font-size:x-small;">
            Click the "Show Spoiler" Button to reveal hidden text.
        </div>
    </div>