The Dink Network

Can anyone tell me how to do collapseable html lists?

<select name="select" size="1">
<option>dfg</option>
<option>fd</option>
<option>gf</option>
<option>d</option>
<option>d</option>
<option>f</option>
<option>df</option>
<option>d</option>
<option>f</option>
<option>fd</option>
<option>d</option>
<option>d</option>
<option>f</option>
</select>

Thanks. I apprecaite it. I'll credit you for this help when I release the thing I'm using it for.