CSS Form builder does not support ASP pages.
To apply server validation to an ASP page, you would need to have the previous version of Validation Toolkit installed.
Validation Toolkit and CSS Form builder cannot be installed at the same time.
The simplest way to work around this issue is to create a new computer user.
Log into this new computer user and uninstall validation toolkit under the new user.
You will need to recreate your Dreamweaver site definition under the new computer user.