title: Update panel not showing errors in ASP.NET 3.5
body: <p>In Visual Studio 2008 if you create a new "Ajax 1.0 Enabled ASP.NET 2.0 Web Application" and paste the following code:</p>
  
  <pre><code>&lt;form id="form1" runat="server"&gt;
          &lt;asp:ScriptManager ID="ScriptManager1" runat="server" /&gt;
          &lt;div&gt;
          &lt;asp:UpdatePanel ID="UpdatePanel1" runat="server"&gt;
              &lt;ContentTemplate&gt;
                  &lt;asp:Button runat="server" ID="foo" Text="click me" onclick="foo_Click" /&gt;      
              &lt;/ContentTemplate&gt;
          &lt;/asp:UpdatePanel&gt;
          &lt;/div&gt;
      &lt;/form&gt;
  </code></pre>
  
  <p>code behind</p>
  
  <pre><code>protected void foo_Click(object sender, EventArgs e) {
              throw new Exception("hello");
          }
  </code></pre>
  
  <p>and then click the button, you'll see a javascript alert that says "hello". If you create a .NET 3.5 Web Application and paste the same code in, no alert shows up anymore. What am I missing?</p>