Rule number 1 when working with forms:
- All Form processing must occur on the forms action page.
The action of the form on your index page is to post to the conformation page:
action="confirmation.php"
The seerver validation behavor needs to be added to the action page.
this tutorial:
http://www.webassist.com/tutorials/Add-server-validation-to-your-web-forms
goes through adding validation to your form pages, it uses the example of a checkout page that posts to a confirm page, use that tutorial for an example of adding validation to a form that posts to another page.