Form markup.
WHAT EVERY FORM NEEDS
The correct method The request protection token Labels associated with fields Sensible field types
WHAT HAPPENS WITHOUT THE TOKEN
The submission is rejected.
That is the framework protecting you, not a fault.
WHAT TO USE FOR METHODS BEYOND THE BASIC TWO
The method field the framework provides, since browsers support only two directly.
WHAT TO REPOPULATE
Every field, with what was previously entered.
WHY
Losing entered data on a validation failure is the most damaging thing a form can do.
WHAT TO DISPLAY
Errors beside each field, and a summary where there are several.
WHAT TO SET FOR MOBILE
Appropriate input types, so the correct keyboard appears.
WHAT TO NAME FIELDS
Consistently with your validation rules and model attributes.
WHY
Mismatches produce validation that never triggers or never passes.
WHAT TO EXTRACT
Repeated field markup, into a component.
WHAT TO TEST
Submitting with everything empty, and with everything wrong.
