People who cannot see forms will find them particularly tricky. People with cognitive or mobility issues who find typing difficult and time consuming will also find forms difficult. Therefore, you should offer the option of backtracking or double checking information. This applies particularly when forms involve personal details such as credit card numbers or bank accounts.
Ideally, if information is not a security risk a site should make suggestions for misspellings or fields filled out incorrectly.
The spider can indicate if a form exists.
Points -
Three points - provide suggestions before submission so user can edit.