请问一个js有关问题 _JavaScript

请教一个js问题
code=JScript]document.getElementById("zhang").innerHTML.substr(0, 2).style.color = col[i] col[0] = '#FFFFFF'; [/code]
<div id="zhang" onclick="Over()">abcdeggsdf></div>
我想更改id为 zhang的 div层的里边值的前2个即abcdeggsdf中的ab的颜色为某一颜色要怎么搞

------解决方案--------------------

HTML code



<!DOCTYPE HTML>
<html>
    <head>
        <meta charset="gb2312" />
        <title></title>    
        <style>
        </style>        
    </head>
    <body>
        <div id="zhang" onclick="Over(this)">abcdeggsdf></div>
        <script>
            function Over(o){
                o.innerHTML = '<span style="color:red;">'+o.innerHTML.substring(0,2)+'</span>'+o.innerHTML.substring(2, o.innerHTML.length);
            }
        </script>
    </body>
</html>