FindControl results in null reference
<p>I have anchor tags like this</p>

<pre><code> &lt;div id="menu_container"&gt;
            &lt;ul id="nav-bar"&gt;
                &lt;li&gt;&lt;a href="Default.aspx" runat="server" id="menu_item_default"&gt;Home&lt;/a&gt;&lt;/li&gt;
                &lt;li&gt;&lt;a href="Account.aspx" runat="server" id="menu_item_account" &gt;Account&lt;/a&gt;&lt;/li&gt;
                &lt;li&gt;&lt;a href="Servers.aspx" runat="server" id="menu_item_servers"&gt;Servers&lt;/a&gt;&lt;/li&gt;
                &lt;li&gt;&lt;a href="Statistics.aspx" runat="server" id="menu_item_statistics"&gt;Statistics&lt;/a&gt;&lt;/li&gt;
                &lt;li&gt;&lt;a href="Tutorials.aspx" runat="server" id="menu_item_tutorials"&gt;Tutorials&lt;/a&gt;&lt;/li&gt;
                &lt;li&gt;&lt;a href="Contact.aspx" runat="server" id="menu_item_contact"&gt;Contact us&lt;/a&gt;&lt;/li&gt;
                &lt;div id="login_registration_container"&gt;
                    &lt;a href="#" id="login"&gt;Sign in&lt;/a&gt; / &lt;a href="Registration.aspx" id="register"&gt;Register&lt;/a&gt;
                &lt;/div&gt;
            &lt;/ul&gt;
        &lt;/div&gt;
</code></pre>

<p>I want to change the CSS class for <code>menu_item_default</code> this way: </p>

<pre><code>WebControl wc = (WebControl)FindControl("#menu_item_default");
wc.Attributes.Add("class", "value");
</code></pre>

<blockquote>
  <p>error: null reference exception</p>
</blockquote>

<p>How can this be done?</p>
