 <p><strong>Turn on tracing</strong></p> <p>You can <a href="http://msdn.microsoft.com/en-us/library/94c55d08.aspx" rel="nofollow noreferrer">turn on tracing</a> on a single page using the Trace attribute in the Page directive. </p> <pre><code>&lt;%@ Page Trace="true" %&gt; </code></pre> <p>You can also <a href="http://msdn.microsoft.com/en-us/library/0x5wc973.aspx" rel="nofollow noreferrer">turn on tracing for all pages</a> in an asp.net application using the web.config setting. </p> <pre><code>&lt;configuration&gt; &lt;system.web&gt; &lt;trace enabled="true" pageOutput="false" requestLimit="40" localOnly="false"/&gt; &lt;/system.web&gt; &lt;/configuration&gt; </code></pre> <p><strong>Add custom output to the trace output.</strong> </p> <pre><code>public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Trace.Write("custom start"); System.Threading.Thread.Sleep(2000); Trace.Write("custom end"); } } </code></pre> <p>The above code shows up like this </p> <p><img src="https://i.stack.imgur.com/7hHwP.png" alt="enter image description here"></p>