Favorite visual means to indicate form validation errors?

[Grant Rettke]

For NG users, there are a multitude of ways to indicate form
validation error. The sky is really the limit here.

I'm wondering, do you have a particular favorite, and why, or why not?

The NG docs have one very colorful way here:
http://docs.angularjs.org/guide/forms

Surely there are others that are loved.

[Sam Pepose]

I personally like how Bootstrap handles invalid form inputs: http://twitter.github.io/bootstrap/base-css.html#forms

It's subtle, yet lets the user know that something is wrong. Couple that with one of their error alerts, and it's a perfect notification.

Yet, Bootstrap has it's own look and feel to it that doesn't work for every theme and UI. If you're looking for something more generic, I would tinker with their LESS.