<com:TContent ID="Content"> <h3>TCustomValidator not enabling ControlCssClass or prop:ClientSide.OnValidationError after postback.</h3> <style> .required { border: 1px solid red; background-color: pink; } </style> <script type="text/javascript"> function clientSideCustomValidate(sender, param) { return param == "Prado"; } </script> <com:TTextBox ID="textbox1" /> <com:TCustomValidator ID="validator1" ControlToValidate="textbox1" ControlCssClass="required" OnServerValidate="customValidate" ClientValidationFunction="clientSideCustomValidate" ClientSide.OnValidationError="alert('error')" ErrorMessage="must equal to 'Prado'" /> <com:TButton ID="button1" Text="Submit!" /> </com:TContent>