Web and Mobile Application Development
Core concepts
Understand client-server architecture, the request-response cycle, and the roles of HTML (structure), CSS (presentation), and JavaScript (behavior). Know the DOM, events, forms and validation, responsive design (media queries, flexible grids), and accessibility basics. Study HTTP methods, status codes, cookies versus sessions, and the difference between static and dynamic pages.
Server-side concepts include templating, RESTful APIs, JSON, authentication tokens, and the MVC pattern. Database connectivity, ORM basics, and deployment (hosting, domains, HTTPS) matter. For mobile, compare native, hybrid, and cross-platform frameworks, and understand app lifecycle, permissions, and offline storage. Version control with Git (commit, branch, merge) is expected knowledge.
Traps to watch
- Confusing GET (idempotent, data in URL) with POST (data in body).
- Assuming CSS controls behavior; it does not.
- Mixing client-side validation (fast, bypassable) with server-side validation (authoritative).
- Believing responsive design equals separate mobile sites; it uses one adaptive layout.
Worked example
A login form validates an email with a JavaScript regex, then submits via POST over HTTPS. If validation exists only in JavaScript, an attacker can disable it, so the server must re-validate. Rule of thumb: client-side validation improves user experience; server-side validation enforces security.