select multiple displaying scrollable list, not a dropdown

[mgm_03]

Instead of displaying a drop-down menu, my form (in FF) is showing a scrollable list. I do want to allow multiple options.

<select name="county_code[]" size="1" multiple>
<option value="">-Select County(s)-</option>
<option value="57" >Dallas</option>
<option value="61" >Denton</option>
<option value="70" >Ellis</option>
<option value="126" >Johnson</option>
<option value="127" >Parker</option>
<option value="127" >Tarrant</option>
<option value="127" >Wise</option>
</select>

[Tyssen]

You can't have multiple options with just a single dropdown.