W3

<SELECT multiple size=4 name=choice-select> note: no value on select
      <OPTION selected value=choice_1_a>choice_1
      <OPTION selected value=choice_1_b>choice_2
      <OPTION>                          choice_3
      <OPTION>                          choice_4
      <OPTION>                          choice_5
      <OPTION>                          choice_6
      <OPTION>                          choice_7
   </SELECT>

<SELECT       size=4 name=selectB>
      <OPTION>       choice_1
      <OPTION>       choice_2
      <OPTION>       choice_3
      <OPTION>       choice_4
      <OPTION>       choice_5
      <OPTION>       choice_6
      <OPTION>       choice_7
   </SELECT>
 <SELECT name=ComOS  size=7>
     <OPTION selected value=none>None</option>*
     <OPTGROUP label=A>
       <OPTION value=A1>A1
       <OPTION value=A2>A2
       <OPTION value=A3>A3
     </OPTGROUP>
     <OPTGROUP label=B>
       <OPTION  value=B1>B1
       <OPTION  value=B2>B2
     </OPTGROUP>
     <OPTGROUP label=C>
       <OPTION  value=C1>C1
       <OPTION  value=C2>C2
     </OPTGROUP>
 </SELECT>


Note: reload will NOT de-select selections, you must use a submit type=reset
Use of
SHIFT to select a range and
CTRL to select multiple choices
scrolling are all implemented