Unlock the Secrets of Domains, HTML, and HTTP: A Complete Web Fundamentals Guide
This comprehensive guide explains domain name concepts, structures, and registration, introduces web page fundamentals and HTML basics—including tags, syntax, and HTML5 features—then covers HTTP protocol essentials, request/response formats, version evolution, and HTTPS security, providing a solid foundation for modern web development.
Domain Names
Domain Name (Domain Name) is a human‑readable string that identifies a website, server or other network resource, replacing numeric IP addresses such as 172.217.14.206. It serves as a “door number” and is resolved to an IP address by the DNS system.
Structure
Domain names use a hierarchical, dot‑separated format (e.g., mail.example.com) consisting of:
Top‑Level Domain (TLD) : the right‑most part such as .com, .org, .cn. TLDs are divided into generic (gTLD) and country code (ccTLD) categories.
Second‑Level Domain (SLD) : the label directly left of the TLD, e.g., example in example.com, which can be registered by users.
Subdomain : an optional leftmost label, e.g., mail in mail.example.com, often used to separate site functions.
Types
By hierarchy: TLD, SLD, subdomain.
By usage: generic ( .com, .net), industry ( .edu, .gov), geographic ( .nyc, .paris), brand ( .google).
Special: Internationalized Domain Names (IDN) supporting non‑Latin characters, reserved names such as localhost.
Registration & Management
Registration process : users query a registrar (e.g., GoDaddy, Alibaba Cloud), provide verified owner information, and pay an annual fee.
Managing bodies : ICANN governs the global DNS system; national bodies (e.g., CNNIC for .cn) manage country‑specific domains.
Privacy protection : optional WHOIS privacy hides personal data.
Web Pages and HTML
Web page (Web Page) is the information carrier accessed via a browser, composed of text, images, video, and links, and built on HTML (HyperText Markup Language).
Core Characteristics
Identified by a URL such as https://www.example.com/page.html.
Accessible on multiple platforms (PC, mobile, tablet).
Can be static (fixed content) or dynamic (generated per request).
HTML Basics
HTML defines the structure and semantics of a page. It works together with CSS for styling and JavaScript for interactivity.
Document Skeleton
<!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>Tag Classification
Semantic tags (HTML5): <header>, <nav>, <section>, <article>, <footer>.
Content tags : <h1> – <h6>, <p>, <ul>, <ol>, <a href="...">, <img>, <table>.
Functional tags : <form>, <input>, <video>, <audio>, <div>, <span>.
Syntax Rules
Tags are enclosed in angle brackets, e.g., <tag>.
Most tags have opening and closing pairs, e.g., <p>content</p>.
Self‑closing tags such as <img src="..."> do not need an end tag.
Attributes provide additional information, e.g.,
<a href="https://example.com" target="_blank">Link</a>.
HTML5 New Features
Additional semantic tags ( <article>, <section>, <nav>).
Native <video> and <audio> support. <canvas> for graphics and games.
Enhanced form controls: new input types ( email, date, range) and attributes ( placeholder, required).
Local storage APIs ( localStorage, 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 and other resources on the Web.
Core Characteristics
Stateless: each request is independent.
Connectionless (HTTP/1.0) or persistent (HTTP/1.1).
Plaintext by default; HTTPS adds TLS encryption.
Flexible: can carry any MIME type.
Workflow
Client creates an HTTP request from a URL.
TCP three‑way handshake establishes a connection.
Server processes the request (e.g., database query).
Server returns an HTTP response with status code and payload.
Connection is closed via four‑way handshake (unless kept alive).
Request & Response Structure
Request Example
GET /index.html HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0
Accept: text/html
Cookie: session_id=abc123Common methods: GET, POST, PUT, DELETE.
Response Example
HTTP/1.1 200 OK
Content-Type: text/html
Set-Cookie: session_id=abc123
Content-Length: 1024
<!DOCTYPE html>
... (HTML content) ...Status code categories: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error.
Version Evolution
HTTP/1.0 – one request per TCP connection.
HTTP/1.1 – persistent connections, Host header, pipelining.
HTTP/2 – binary framing, multiplexing, header compression, server push.
HTTP/3 – built on QUIC (UDP) to eliminate head‑of‑line blocking.
HTTPS
Encryption via TLS/SSL protects confidentiality and integrity.
Server presents a digital certificate issued by a CA for identity verification.
Default port is 443 (instead of 80 for plain HTTP).
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