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- A form must have a visible submit button with a meaningful label.
- Interactions with form fields (checking a checkbox, making a selection selecting in a comboboxcombo box) should not trigger the submission of the form because that is not predictable.
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- It should be clear for all users whether the form was successfully submitted or not: use text to give this feedback (not only colorcolour) and make sure the feedback is visible for everyone (manage focus if needed).
- Error messages should specify the nature and location of the errors. They can be located at the top of the form or inline. Make sure the fields to be corrected stand out: don’t use only colorcolour.
For forms containing personal data or financial information, make sure the user can double check the information before submitting, or correct the information after submission.
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Avoid using graphical or audio captchas to block SPAM. Many users will not be able to decipher decipher the code they have to copy.
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For more information about avoiding CAPTHA’s, read CAPTCHA-less secuity security by Karl Groves