ASP+ contains a series of validator controls to aid in server-side form validation. These controls include:
RequiredFieldValidator- Used to ensure that a form field has a value entered
CompareValidator- Used to ensure that a form field entry is equivalent to another form control
RegularExpressionValidator- Used to ensure that a form field entry conforms to a particular regular expression
RangeValidator- Used to ensure that a form field entry has a value between a certain range
CustomValidator- Allows you to build your own validation logic to compare a form field value against
ValidationSummary- Used to display a summary of validation errors
To learn all about form validation with ASP+, be sure to read: Form Validation with ASP+! Also, you can view the validator control technical docs!