HTML给select添加placeholder的技巧

<select>  
    <option value='' disabled selected style='display:none;'>Please Choose</option>  
    <option value=''>Open when powered (most valves do this)</option>  
    <option value=''>Closed when powered, auto-opens when power is cut</option>  
</select>

<select>  
   <option value="" disabled selected>Select your option</option>  
   <option value="hurr">Durr</option>  
</select>