Course 10 · Foundation
The Web
What happens between the click and the pixel.
DNS, TCP, TLS, HTTP, caching, cookies, CORS and the rendering pipeline — the layer every framework sits on and nobody teaches.
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The syllabus
18 lessons,
in the order they build on each other.
A URL, and finding the server
Every part of a URL, what DNS actually answers, and why the first request is the slow one.
TCP, TLS and the handshake
What is set up before a single byte of your request is sent, and what HTTPS does and does not protect.
The request and the response
Methods, paths, versions, status codes — the anatomy of both messages, byte by byte.
The headers that matter
Content type, length, encoding, language, and the ones that change how the browser behaves.
Redirects
301, 302, 303, 307, 308 — which ones change the method, and which ones are forever.
Caching
Cache-Control, freshness, immutable assets, and why your users still see last week’s CSS.
Conditional requests
ETag, Last-Modified and the 304 that sends no body at all.
Cookies
Attributes, scope, SameSite, and exactly which requests carry them.
CORS
The rule the browser enforces, the preflight, and why the error is never in your JavaScript.
Authentication over HTTP
Sessions, tokens, where to keep them, and what each choice costs you.
Security headers
HSTS, CSP, frame options, referrer policy — a few lines that close whole categories of attack.
HTTP/2 and HTTP/3
Multiplexing, head-of-line blocking, and which old performance advice is now wrong.
How a page is rendered
Parse, CSSOM, layout, paint, composite — and what forces each stage to run again.
The critical path
What blocks the first paint, and the handful of tags that decide how fast a page feels.
The event loop
Tasks, microtasks, rendering, and the long task that makes a page feel broken.
Where the browser keeps things
Cookies, localStorage, IndexedDB, the Cache API — size, lifetime, and who can read them.
Service workers and offline
A proxy you write, the cache strategies worth knowing, and how to avoid shipping a broken one.
Practice: read a waterfall
One slow page, one network panel, and the five questions that find the cause.
Keep going
The other courses.
HTML
The document, the elements and the meaning behind them. Everything else on the web is layered on top of this.
CSS
Selectors, the box model, layout with flexbox and grid, and motion that has a reason to move.
JavaScript
Values, functions, the DOM, events and asynchronous work — written so you can debug it later.