css中指定下拉列表在firefox中的宽度两种写法

<select name="ddlDept" id="ddlDept" style="width:80px;">
<option>上海 - 物业资讯部</option>
<option>北京 - 物业资讯部</option>
<option>重庆 - 物业资讯部</option>
<option>深圳资讯科技部</option>
<option>电脑部</option>
</select>

<select name="ddlDept" id="ddlDept" style="width:80px;overflow-x:hidden;">
<option style="width:80px;overflow-x:hidden;">上海 - 物业资讯部</option>
<option style="width:80px;overflow-x:hidden;">北京 - 物业资讯部</option>
<option style="width:80px;overflow-x:hidden;">重庆 - 物业资讯部</option>
<option style="width:80px;overflow-x:hidden;">深圳资讯科技部</option>
<option style="width:80px;overflow-x:hidden;">电脑部</option>
</select>

<style type="text/css">
#ddlDept{width:80px;overflow-x:hidden;}
#ddlDept option{width:80px;overflow-x:hidden;}
</style>
<select name="ddlDept" id="ddlDept">
<option>上海 - 物业资讯部</option>
<option>北京 - 物业资讯部</option>
<option>重庆 - 物业资讯部</option>
<option>深圳资讯科技部</option>
<option>电脑部</option>
</select>