字体大小随机问题

[我是地摊小贩]

    /// <summary>
    /// 这是页面加载事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void Page_Load(object sender, EventArgs e)
    {
        GetKeyword();
    }
    /// <summary>
    /// 得到关键字的方法
    /// </summary>
    public void GetKeyword()
    {
        string keyword = "";
        CacheManager.Cachetype = CacheType.middle;
        Control.DBTypes = DbTypes.madeinchina;
        DataSet ds = Control.GetValue(SqlManager.GetKeyWord(ShangjiaID, Endnumber));
        int Count = ds.Tables[0].Rows.Count;
        for (int i = 0; i < Count; i++)
        {
            keyword = Convert.ToString(ds.Tables[0].Rows[i]["articlekeyword"]);
            Literal1.Text += "<a class=\"f" + Getstochastic() + "\" href='javascript:;' onclick='javascript:var key=encodeURI(\"" + keyword + "\");window.open(\"list_k" + HttpUtility.UrlEncode(keyword) + ".html\");'  style=\"margin-right:5px;\">" + keyword + "</a>";
        }
    }
    /// <summary>
    /// 这是得到随机样式的方法
    /// </summary>
    /// <returns></returns>
    public string Getstochastic()
    {
        int number = 0;
        Random rd = new Random();
        number = rd.Next(12, 21);
        return number.ToString();
    }

为什么我在页面显示的时候昨天大小都是一样的，在调试完以后字体大小不同，请各位高手看看

[我是地摊小贩]

求高手啊................

[我是地摊小贩]

急急急急啊。。。。救命啊。。。。。。。

[threenewbee]

public string Getstochastic()
{
int number = 0;
Random rd = new Random();
number = rd.Next(12, 21);
return number.ToString();
}

=>
private Random rd = new Random();

public string Getstochastic()
{
int number = 0;
number = rd.Next(12, 21);
return number.ToString();
}