required field validator
<p>i am new to asp.net and i am setting required field validator and it is showing me an error</p>

<p><strong>error is:</strong></p>

<pre><code>Unable to find control id 'txtFirstName' referenced by the 'ControlToValidate' property of 'RequiredFieldValidator1'. 
</code></pre>

<p><strong>code is:</strong></p>

<pre><code> &lt;tr&gt;
            &lt;td align="right" style="padding-right: 5px; width: 50%;"&gt;
                &lt;asp:Label ID="lblFirstName" runat="server" Text="FIRSTNAME :"&gt;&lt;/asp:Label&gt;
            &lt;/td&gt;
            &lt;td align="left" style="padding-left: 5px; width: 50%;"&gt;
                &lt;asp:TextBox ID="txtFistName" runat="server" Width="70%"&gt;&lt;/asp:TextBox&gt;
                &lt;asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txtFirstName" ErrorMessage="You can't leave this empty."&gt;&lt;/asp:RequiredFieldValidator&gt;
            &lt;/td&gt;

        &lt;/tr&gt;
</code></pre>

<p>can any help me on this flow....,</p>
