Understanding Domain Names, HTML, and HTTP: A Complete Beginner’s Guide
This article explains the concept, structure, and types of domain names, the fundamentals of web pages and HTML—including document structure, tags, and HTML5 features—as well as the core principles, workflow, request/response formats, version evolution, and security extensions of the HTTP protocol.
Web Technology and HTTP Protocol
Domain Name (Domain Name) is a human‑readable string that identifies a website or network resource, replacing numeric IP addresses such as 172.217.14.206. It serves as a “door number” for users and is resolved to an IP address via the DNS system.
Core role : provides an easy‑to‑remember address and maps to IP addresses through DNS.
Structure : hierarchical, separated by dots (e.g., mail.example.com).
Components :
Top‑Level Domain (TLD) : the right‑most part (e.g., .com, .org, .cn). Includes generic TLDs (gTLD) and country‑code TLDs (ccTLD).
Second‑Level Domain (SLD) : the label directly left of the TLD (e.g., example in example.com).
Subdomain : additional labels to the left (e.g., mail in mail.example.com).
Types :
By hierarchy: traditional gTLDs, new gTLDs, ccTLDs.
By purpose: generic (.com, .net), industry (.edu, .gov), geographic (.nyc, .paris), brand (.google, .apple).
Special: Internationalized Domain Names (IDN) supporting non‑Latin characters, reserved names like localhost.
Registration and Management :
Register through domain registrars (e.g., GoDaddy, Alibaba Cloud) after identity verification.
Managed globally by ICANN and locally by national authorities (e.g., CNNIC for .cn).
Privacy protection can hide WHOIS information.
Web Pages and HTML
Web Page (Web Page) is an information carrier accessed via a browser, composed of text, images, video, and hyperlinks, built on HTML (HyperText Markup Language).
Core characteristics : identified by a URL, accessible across devices, can be static (fixed content) or dynamic (generated by a server).
HTML Basics
HTML defines the structure and semantics of web content through tags. It works together with CSS for styling and JavaScript for interactivity.
Core Functions
Describes document structure (headings, paragraphs, lists, etc.).
Embeds multimedia (images, audio, video) and hyperlinks.
Combined with CSS and JavaScript to build complete front‑end pages.
Basic Document Structure
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Page Title</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
<img src="image.jpg" alt="Image description">
<script src="script.js"></script>
</body>
</html>HTML Tag Classification
Semantic tags (HTML5): <header>, <nav>, <section>, <article>, <footer>.
Content tags : headings ( <h1> ‑ <h6>), paragraphs ( <p>), lists ( <ul>, <ol>), tables ( <table>).
Functional tags : forms ( <form>), inputs ( <input>), media ( <video>, <audio>), containers ( <div>, <span>).
Static vs. Dynamic Pages
Static : server returns pre‑generated HTML files; only HTML/CSS/JS needed; updates require manual file changes.
Dynamic : server generates HTML per request using backend languages and databases; supports real‑time data, user input, and complex interactions.
HTML5 New Features
Semantic tags : <article>, <section>, <nav>, etc., improve readability and SEO.
Multimedia support : native <video> and <audio> tags.
Graphics and animation : <canvas> for drawing and games.
Form enhancements : new input types (email, date, range) and attributes (placeholder, required).
Local storage : localStorage and sessionStorage replace cookies for client‑side data.
HTTP Protocol
HTTP (HyperText Transfer Protocol) is an application‑layer protocol based on the client‑server model, used to transfer hypertext such as HTML, images, and other resources on the web.
Stateless : each request is independent; state is maintained via cookies or sessions.
Connection‑less (early HTTP/1.0) and persistent connections in HTTP/1.1.
Plain‑text transmission ; HTTPS adds TLS/SSL encryption.
Flexibility : can carry any data type via the Content‑Type header.
Workflow
Client creates an HTTP request from a URL.
TCP connection is established (three‑way handshake).
Server processes the request (e.g., database query, file read).
Server returns an HTTP response with status code and payload.
Connection is closed (four‑way handshake) unless persistent.
Request and Response Structure
GET /index.html HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0
Accept: text/html
Cookie: session_id=abc123Common methods include GET, POST, PUT, DELETE, etc.
HTTP/1.1 200 OK
Content-Type: text/html
Set-Cookie: session_id=abc123
Content-Length: 1024
<!DOCTYPE html>
<html>...</html>Status code categories: 1xx: informational (e.g., 101 Switching Protocols). 2xx: success (e.g., 200 OK, 201 Created). 3xx: redirection (e.g., 301 Moved Permanently). 4xx: client error (e.g., 404 Not Found). 5xx: server error (e.g., 500 Internal Server Error).
Version Evolution
HTTP/1.0 : simple, one request per TCP connection.
HTTP/1.1 : persistent connections, pipelining, Host header for virtual hosting.
HTTP/2 : binary framing, multiplexing, header compression, server push.
HTTP/3 : built on QUIC (UDP), eliminates head‑of‑line blocking.
HTTPS (Secure HTTP)
Encryption : TLS/SSL encrypts HTTP payload to prevent eavesdropping and tampering.
Authentication : server presents a digital certificate issued by a Certificate Authority (CA).
Default port : 443 (instead of HTTP’s 80).
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Raymond Ops
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