Invalid postback or callback argument
<p>I had web site I launched it on server and it worked well internal but when it being online this error appear in registration form</p>

<blockquote>
  <p><code>&lt;error&gt;</code></p>
  
  <p>Invalid postback or callback argument.  Event validation is enabled using <code>&lt;pages enableEventValidation="true"/&gt;</code> in configuration or <code>&lt;%@ Page EnableEventValidation="true" %&gt;</code> in a page.  For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  If the data is valid and expected, use the <code>ClientScriptManager.RegisterForEventValidation</code> method in order to register the postback or callback data for validation. </p>
</blockquote>
