Select Field with Options Group Name

<select name="myselectbox">
   <option value="please select">
      <optgroup label="this is group one">
         <option value="groupone_one>
         <option value="groupone_two>
         <option value="groupone_three>
     </optgroup>
     <optgroup label="this is group two">
         <option value="grouptwo_one>
         <option value="grouptwo_two>
         <option value="grouptwo_three>
     </optgroup>
</select>