因为Select下拉框只支持disabled属性，不支持readOnly属性，

而在提交时，disabled的控件，又是不提交值的，在网上搜索了一下，发现有个很好的方法：

<select onmouseover="this.releaseCapture();" name="select123" onfocus="this.blur();"> <option selected="selected">aaa</option></select>
<select onmouseover="this.releaseCapture();" name="select123" onfocus="this.blur();"> <option selected="selected">aaa</option></select>

或者使用如下的js脚本：

<select name="select123"> <option selected="selected">aaa</option></select>

<script type="text/javascript">// <![CDATA[

SetReadOnly(document.getElementById("select123"));   
function SetReadOnly(obj){   
    if(obj){   
         obj.onbeforeactivate = function(){return false;};   
         obj.onfocus = function(){obj.blur();};   
         obj.onmouseover = function(){obj.setCapture();};   
         obj.onmouseout = function(){obj.releaseCapture();};   
     }   
}   

// ]]></script>