Uncommon XHTML Tags, Part 8

The <optgroup> </optgroup> tag groups up the <option> </option> tag to show their relation. The name of the option group cannot be selected in the drop down list; only the options can be selected.

For example:
<select>
<optgroup label="Vowels">
<option value="A">A</option>
<option value="E">E</option>
</optgroup>
</select>

becomes:



A
E