How Websites Work

A physicist wanted to share his research papers

In 1989, Tim Berners-Lee was a software engineer at CERN, the European physics lab. He had a problem: thousands of scientists were producing research, but nobody could find anyone else's work. Documents were scattered across incompatible computers with no way to link them together.

So he wrote a proposal. His boss scribbled "Vague but exciting" on the cover page and let him run with it. Within two years, Berners-Lee had invented three things: HTML (a way to write documents), URLs (a way to address them), and HTTP (a way to transfer them). He called the system the World Wide Web.

That "vague but exciting" memo became the foundation of a system that now serves over 1.1 billion websites.

By the end of this module, you'll have a complete mental model of how every website works — the request-response cycle, URL anatomy, HTTP status codes, and the rendering pipeline. You'll use browser DevTools to watch this invisible machinery in real time.

The internet vs. the web — they're not the same thing

Most people use "internet" and "web" interchangeably. They're actually different layers.

The internet is the physical infrastructure — cables, routers, satellites, and protocols that let computers talk to each other. It existed since the 1960s (as ARPANET).

The web is a service that runs on top of the internet, using HTTP to deliver pages you view in a browser. Email, streaming video, and online gaming also run on the internet — but they're not the web.

There Are No Dumb Questions

If the web runs on the internet, could the internet exist without the web?

Absolutely. The internet existed for 20 years before the web was invented. The internet is the road system; the web is one type of vehicle driving on it.

What about apps on my phone — are those the web?

Some are, some aren't. A website opened in Safari is the web. A native app like WhatsApp uses the internet but speaks its own protocols. Many apps are hybrids — they look native but load web content behind the scenes.

What happens when you type a URL and press Enter

Every time you visit a website, an invisible conversation happens between your browser and a server somewhere in the world. The whole thing takes milliseconds, but there are several steps.

This is the request-response cycle — the fundamental pattern of the entire web.

URLs: the address system of the web

Every page on the web has a unique address — its URL (Uniform Resource Locator). Understanding URL structure is foundational.

https://www.shop.example.com:443/products/shoes?color=red&size=10#reviews

There Are No Dumb Questions

What's the difference between HTTP and HTTPS?

The "S" stands for Secure. HTTPS encrypts all data between your browser and the server so nobody in between can read it. In 2026, virtually all legitimate websites use HTTPS. Browsers now warn you if a site uses plain HTTP.

Do I need to type https://www every time?

No. Browsers are smart enough to add these for you. But understanding the full structure helps when you're building websites and debugging issues.

The three languages of every webpage

Every webpage you've ever seen is built with three technologies working together:

Here's how they work together on a simple button:

<!-- HTML: defines that a button exists -->
<button class="buy-btn">Add to Cart</button>

/* CSS: makes the button look good */
.buy-btn {
  background-color: #4CAF50;
  color: white;
  padding: 12px 24px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
}

// JavaScript: makes the button do something
document.querySelector('.buy-btn').addEventListener('click', function() {
  alert('Item added to your cart!');
});

HTTP status codes: the server talks back

When your browser makes a request, the server always responds with a status code — a three-digit number that tells you what happened.

You've definitely seen a 404 page before. Now you know exactly what it means: your browser asked for something, and the server said "I don't have that."

Client vs. server: who does the work?

In web development, you'll constantly hear "client-side" and "server-side." This is simply about where the code runs.

Front-end development = building the client side (HTML, CSS, JavaScript). Back-end development = building the server side (databases, APIs, logic). Full-stack development = doing both.

How a modern webpage actually loads

When your browser receives the HTML response, it doesn't just display it. It goes through a precise rendering process:

There Are No Dumb Questions

Why does JavaScript run last?

Because JavaScript can change anything on the page. The browser wants a stable foundation (HTML parsed, CSS applied) before JavaScript starts manipulating things. That's why you'll often see <script> tags at the bottom of HTML files.

From Tim's memo to your career

Tim Berners-Lee could have patented the web. He didn't. He gave it away for free, insisting it should remain open and accessible to everyone. That decision is the reason you can learn to build websites without paying anyone for the right to publish on the internet. The technologies he created in 1991 — HTML, URLs, HTTP — are still the foundation of every single website, including the one you're reading right now.

You now understand the invisible machinery behind every page load: DNS resolves a domain, your browser sends an HTTP request, the server responds with HTML, and the browser renders pixels on your screen. That mental model will serve you for your entire career.

Next up: In the next module, you'll write your first HTML — the same markup language Berners-Lee invented in 1991 — and watch a page appear in your browser. You'll go from understanding how websites work to building one.

Key takeaways

• The internet is the infrastructure; the web is a service running on top of it using HTTP
• Every webpage involves a request-response cycle: browser asks, server answers
• URLs are structured addresses with protocol, domain, path, and query parameters
• HTML provides structure, CSS provides style, JavaScript provides interactivity
• HTTP status codes (200, 301, 404, 500) tell you what happened with your request
• DNS translates human-readable domain names into IP addresses
• Front-end = browser side, back-end = server side, full-stack = both