HTML Multiple Select option group

<select name= "ViewType" style= "width:100%;height:300px;" multiple= "multiple" >
    <option value selected> Select sort/display mode </option>
    <optgroup label= "Sort" >
        <option> by price from low to high </option>
        <option> by price from high to low </option>
        <option> by time remaining from less to more </option>
        <option> by the time remaining from the many to less </option>
    </optgroup>
    <optgroup label= "Display" >
        <option> List Mode </option>
        <option> Image </option>
        <option> Plain Text mode </option>
    </optgroup>
    <optgroup label= "Quantity" >
        <option> Show 20 </option> per page
        <option> Show 40 </option> per page
        <option> Show 80 </option> per page
    </optgroup>
</select>

HTML Multiple Select option group