Lesson 7: Security, Accessibility, Performance, and Testing

Even a simple web app can expose users to risk if security is ignored. At the introductory level, you should recognize some common concerns:

• weak authentication,
• unsanitized user input,
• unauthorized access,
• insecure file uploads,
• exposed sensitive data.

Two foundational habits matter immediately:

• validate and sanitize input
• enforce authorization rules

For example, if a user edits the URL to view another student's private record, the server should still block access when permission is missing. Security cannot depend on the honesty of the user interface.

You are not expected to master all web vulnerabilities in one lesson, but you should understand that security is part of design, not a last-minute patch.

Accessibility means building websites that can be used by more people, including users with disabilities or temporary limitations.

Important accessibility practices include:

• meaningful HTML structure,
• keyboard-friendly interaction,
• sufficient color contrast,
• descriptive form labels,
• alt text for informative images,
• visible focus states.

Accessibility is not "extra polish." It directly affects usability and fairness. A government service portal, scholarship page, or university enrollment system should be usable even without a mouse or with assistive technology.

In many cases, semantic HTML already improves accessibility. That is why the earlier lessons matter.