When an error message appears on the page, it becomes part of the layout of the page. You can specify that the layout be fixed — the error message does not change the page layout when it appears — or dynamic. For details about layout options, see Error Message Layout.
To specify fixed or dynamic layout for client error messages
Note Only browsers that support the visible style attribute can make a distinction between static and dynamic layout.
See Also
Validation Controls | Introduction to Validating User Input in Web Forms |