I am building a form that will require a person to be signed in to successfully post. Filling out this for is ESSENTIAL to my web application, so I really want to make it as painless as possible - and, to make it harder, many people will try and fill out this form before they realize they need to have an account and be signed in.
Is it better to:
- Prompt them to sign in / register BEFORE they even get to the form with a lightbox popup (ala Digg).
- Prompt them to sign in / register BEFORE they get to the form with a separate page altogether?
- Allow them to get to the form and present them with a lightbox popup?
- Allow them to get to the form, and add the sign up / register fields to the form itself?