multiselect-master
<select id='pre-selected-options' multiple='multiple'>
<option value='elem_1' selected>elem 1</option>
<option value='elem_2'>elem 2</option>
<option value='elem_3'>elem 3</option>
<option value='elem_4' selected>elem 4</option>
...
<option value='elem_100'>elem 100</option>
</select>