Clarification on error messages for form submission

Hi

I've been reading over the excellent guide on User notifications with forms<https://www.w3.org/WAI/tutorials/forms/notifications/>.

I have a question on where the documentation mentions that:
 "In addition to overall feedback, more specific feedback at or near the form controls can better help users to use your form. This includes feedback to indicate correctly entered input as well as errors in the input."

From the content on the page, it appears that providing inline feedback is best practice. I was wondering, if there are specific WCAG criteria that states that it is bad practice to load a separate page to provide users with feedback (ie that they have submitted an incorrect entry on a form)? If so could this be referenced on the guidance please?

I am auditing a website to feedback to the developer and hopefully they will make required edits and will refer them to the guidance. If there is specific WCAG violations then hopefully the developer will prioritise these. I think their site needs a lot of work - it has the form's errror message on a separate page and worse still, the error message uses a <tr> tag 🙁

Thanks for your advice.

Kind regards,

Nik

Project Opera - Accessibility at Kent
University of Kent
Room GG3B
Keynes College
Canterbury
Kent
CT2 7NP

Kent Inclusive Practices (KIPS)​<https://www.kent.ac.uk/studentsupport/accessibility/inclusive-practice.html>
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