Validation Rules and Standard Controllers

If a user enters data on a Visualforce page that uses a standard controller, and that data causes a validation rule error, the error can be displayed on the Visualforce page. If the validation rule error location is a field associated with an <apex:inputField> component, the error displays there. If the validation rule error location is set to the top of the page, use the <apex:pageMessages> or <apex:messages> component within the <apex:page> to display the error.