<com:TContent ID="Content"> <style> .loader { position:absolute; right:0px; top:0px; color:white; background-color:#900; padding: 0.5em 1em; } input.required { border: 1px solid red; background-color: pink; } </style> <h1>Callback Custom Validator Test</h1> <com:TTextBox ID="text1" /> <com:TActiveCustomValidator ControlToValidate="text1" ErrorMessage="*" ControlCssClass="required" OnServerValidate="validate_text1"> <prop:ClientSide OnValidationError="$('status').innerHTML='Error '+(new Date())" OnValidationSuccess="$('status').innerHTML='Success '+(new Date())" OnLoading="Element.show('loader')" OnComplete="Element.hide('loader')" /> </com:TActiveCustomValidator> <span id="status"></span> <com:TActiveButton Text="Submit" /> <span id="loader" style="display:none;" onfocus="alert('ok')" class="loader">Loading...</span> </com:TContent>