IE8/IE7/IE6下Select列表中disabled的使用

昨天项目中使用select列表list-to-list，其中右边有一项是不可以让用户选中，就是必须选，我使用了selectedFields.options[0].disabled = 'disabled';或者selectedFields.options[0].disabled = true;在IE8下面是正常的，不可选的，但在IE6和IE7下没有起到作用，试了几种方法都不行，最后在网上找到下面代码，只要copy到你的js文件里，然后使用上面的disabled就可以做到不可选的效果了。 
有用到可以看看： 

/****************************************************************
* Author:   Alistair Lattimore
* Website:  http://www.lattimore./
* Contact:  http://www.lattimore./contact/
*           Errors, suggestions or comments
* Date:     30 June 2005
* Version:  1.0
* Purpose:  Emulate the disabled attributte for the <option>
*           element in Internet Explorer.
* Use:      You are free to use this script in non-commercial
*           applications. You are however required to leave
*           this comment at the top of this file.
*
*           I'd love an email if you find a use for it on your
*           site, though not required.
****************************************************************/

window.onload = function() {
    if (document.getElementsByTagName) {
        var s = document.getElementsByTagName("select");

        if (s.length > 0) {
            window.select_current = new Array();

            for (var i=0, select; select = s[i]; i++) {
if(select.id == "your select id") {[//你的select id
select.onfocus = function(){ window.select_current[this.id] = this.selectedIndex; }
                select.onchange = function(){ restore(this); }
                emulate(select);
            [color=red]}[/color]}
        }
    }
}

function restore(e) {
    if (e.options[e.selectedIndex].disabled) {
        e.selectedIndex = window.select_current[e.id];
    }
}

function emulate(e) {
    for (var i=0, option; option = e.options[i]; i++) {
        if (option.disabled) {
            option.style.color = "graytext";
        }
        else {
            option.style.color = "menutext";
        }
    }
}