<tr>
    <td class="tdLabel"><label for="mySelection" class="label">My Selection:</label></td>
    <td class="tdInput">
<select name="mySelection" id="mySelection" multiple="multiple">
    <option value="1">one</option>
    <option value="2" selected="selected">two</option>
    <option value="3">three</option>

<optgroup 
	label="My Label 1"
>

	<option value="11"
	>aaa
	</option>
	<option value="12"
	selected="selected"
	>bbb
	</option>
	<option value="13"
	>ccc
	</option>
</optgroup>
<optgroup 
	label="My Label 2"
>

	<option value="21"
	>ddd
	</option>
	<option value="22"
	selected="selected"
	>eee
	</option>
	<option value="23"
	>fff
	</option>
</optgroup>

</select>
<input type="hidden" id="__multiselect_mySelection" name="__multiselect_mySelection" value=""/>
</td>
</tr>