分组下拉菜单和列表标签：
<select name=" " >
<optgroup label="组1">
<option value="..." >选项</option>
<option value="..." >选项</option>
......
</optgroup>
<optgroup label="组2">
<option value="..." >选项</option>
<option value="..." >选项</option>
......
</optgroup>
......
</select>