Here are the common checklist to use when gathering requirements for a web application.
- Browsers and Future Browser Support (reducing this significantly reduces cost)
- Authentication, Password Reset...
- Number of functions
- Number of screens
- Email Notification
- Server Services
- Client Services
- Authentication Model (User Auth, Grid Card, Multi-Factor, 2-Factor etc...)
- Role/Group based security
- Any legislation for encryption?
- Current number of users and projected growth.
- Special dates where load is increased.
- International users?
- Requires high availability?
- Maintenance windows.