<com:TContent ID="Content">
  <h1>Issue 524 Test</h1>
    <com:TTextBox ID="textbox1" />
    <com:TActiveButton ID="buttonOk" Text="Ok button" />
      <com:TActiveCustomValidator ID="Validator" ControlToValidate="textbox1" OnServerValidate="validateText" Text="Input is invalid." />
</com:TContent>