The validators all share a couple of attributes, which can be very useful in some cases.
This attribute was introduced with ASP.NET 2.0, and makes it possible to divide your form elements into groups. Usually, a validator control is always triggered on a postback, which could sometimes lead to problems. For instance, if you have a contact form and a search field on the same page, the validation of the contact form could be triggered by the Search button, preventing the user from searching before filling out the contact form. You can assign a name in the validationgroup property, for both the validators and the button(s) that you wish to be able to trigger the validation. The value of the attribute can be a number or a name, like validationgroup="contact_form".
This attribute was also introduced with ASP.NET 2.0, and it does exactly what the name implies. Set SetFocusOnError to true on one or several of your validators, to give focus to the first invalid field when the form is validated.
This attribute decides how the validator is rendered to your page. The default value is Static, which makes the validator take up the required place whether it's visible (active) or not. You can test this by placing a piece of text directly behind a validator and load the page. If you have not set the Display attribute, or if you have set it to Static, you will see that the text is moved. However, if you set it to Dynamic, the validator will only take up any space if the validation fails and the validator is activated. This can be convenient in some cases, where you need the space the validator can take up otherwise. If you set it to None, the error message will never be shown.