HTML, CSS & JavaScript: How Web Pages Are Built
Lesson 5: HTML, CSS & JavaScript
When a server sends a webpage to your browser, it doesn’t send a “finished page”.
It sends instructions.
Your browser reads these instructions and builds the page you see.
The Three Core Web Technologies
Every website you visit is built using three core technologies:
- HTML – structure
- CSS – appearance
- JavaScript – behavior
Each one has a different role.
HTML: The Structure
HTML (HyperText Markup Language) defines:
- Headings
- Paragraphs
- Links
- Images
- Forms
Think of HTML as the skeleton of a webpage.
Without HTML, there is nothing to display.
CSS: The Appearance
CSS (Cascading Style Sheets) controls:
- Colors
- Fonts
- Layout
- Spacing
- Animations
CSS is like clothing and design.
HTML says what exists.
CSS says how it looks.
JavaScript: The Behavior
JavaScript makes pages interactive.
It allows websites to:
- Respond to clicks
- Update content without reloading
- Validate forms
- Load data dynamically
JavaScript is the brain of the webpage.
How the Browser Uses Them Together
When your browser receives a webpage:
- It reads the HTML
- It applies CSS styles
- It runs JavaScript code
- It displays the final result
All of this happens very quickly.
What Happens If One Is Missing?
- Without HTML → nothing appears
- Without CSS → page looks plain
- Without JavaScript → page still works, but feels static
This separation is intentional and powerful.
Reflection Question
Think about this:
Why do you think the web was designed using three separate technologies instead of one?
Lesson Summary
- HTML creates structure
- CSS controls appearance
- JavaScript adds behavior
- Browsers combine all three to build webpages
➡️ Next Lesson: What Is a Framework? Why Developers Use Them