The following screenshot shows what happens if we try to submit a new product with none of the fields filled in. Try it by visiting http://localhost:3000/products/new and submitting the form without entering any data. It’s pretty impressive: the fields with errors are highlighted, and the errors are summarized in a nice list at the top of the form.
The fields with errors are not highlighted in the screenshot and neither in the app itself at this point. Also shadows in all screenshots are rendered as a weird mobile-webkit-like outline that ignores the rounded corner’s border radius.