Web control validation may be defined using one or more declarations that are included in an ASP+ file by the web page author. The declarations specify server-side objects that validate the input data received in the web page and provide error handling in the event of a validation failure error. Validation declaration parameters specify the validation criteria against which the input data is validated. Example validation operations involve regular expressions, required fields, data comparison, range comparison and custom validation. Validation parameters can also specify either server-side validation or client-side validation, depending on the client browser's capabilities. In a server-side scenario, a server-side validation object processes the input data received in an HTTP request from the client. In a client-side scenario, a server-side validation object renders the appropriate client-side code to validate the input data without a round trip between the client and the server.