How to make this option?

<select id='signature'>
<option value='null'>Select A Signature</option>
<option value='CFC1'>Combat Arms Classic</option>
<option value='CFC4'>Nuked</option>
<option value='CFC2'>Sniperz Riflez</option>
<option value='CFC3'>I R Pro</option>
<option value='CFC5'>Skull Head</option>
</select>

I have all these options to choose certain signatures. But how do I add an option that you cant click and could be like a category above something.

By using <optgroup> (http://www.w3schools.com/tags/tag_optgroup.asp).

This is an HTML question. Please help us stay organized by posting in the correct category.

Thanks,
Dan