title: Script manager popup doesn't appear
body: <p>I have an ASP.NET page. I want to throw a pop up upon clicking a certain button on the page. The syntax I used is this:</p>
  
  <pre><code>ScriptManager.RegisterStartupScript(this, this.GetType(), "popup", "alert('Invalid Address!!');", true);
  </code></pre>
  
  <p>The popup did not appear. </p>
  
  <p>However, when trying the same syntax on a different page in the same project, it worked. </p>
  
  <p>Any ideas?</p>