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What is HTML: The Complete Expert‘s Guide

HTML (HyperText Markup Language) is the backbone of the web. According to W3Techs, HTML is used by 92.8% of all websites, far ahead of other markup languages. If you‘re interested in web development, learning HTML is absolutely essential.

In this comprehensive guide, we‘ll cover everything you need to know about HTML, diving deep into its history, syntax, usage, and its role in modern web development. Whether you‘re an aspiring web developer or a curious web user, understanding HTML will give you a solid foundation in how the web works.

HTML Overview

HTML is the standard markup language for creating websites and web applications. It uses a special syntax of opening and closing tags to structure the content into headings, paragraphs, sections, images, and other elements.

Here‘s a simple example of some HTML:

<!DOCTYPE html>
<html lang="en">
  <title>My Web Page</title>

  <p>This is a paragraph of text.</p>
    <li>List item 1</li>
    <li>List item 2</li>

This example demonstrates several key aspects of HTML:

  • The <!DOCTYPE html> declaration specifies that this is an HTML5 document
  • The <html> element is the root element of the page
  • The <head> element contains meta information like the page title
  • The <body> element contains the main content of the page
  • Headings are defined with the <h1> through <h6> tags
  • Paragraphs are defined with the <p> tag
  • Unordered lists use the <ul> tag with <li> tags for each list item

When a web browser loads an HTML document, it parses the tags to render the structured content on the screen. The hierarchical nesting of tags creates the document object model (DOM), which is what enables the dynamic manipulation of content with JavaScript.

History of HTML

HTML was invented by Tim Berners-Lee, a physicist at CERN, in 1989-1990 as part of his vision for a global hypertext system based on the Internet. He created the initial HTML tags based on the SGML markup language that was popular in academia.

The first website built with HTML went live in December 1990. Throughout the 1990s, HTML underwent rapid development with new versions:

  • HTML 2.0 (1995) – added basic table support, form elements, and more
  • HTML 3.2 (1997) – added support for fonts, tables, and text flow around images
  • HTML 4.01 (1999) – added support for style sheets, framesets, embedded objects, and scripting

In the 2000s, HTML development bifurcated into XHTML (a stricter XML-based version) and regular HTML. Eventually XHTML lost favor and HTML5 was finalized as a W3C Recommendation in 2014.

HTML5 introduced many new tags (article, header, footer, nav, aside, figure, etc), form elements (date, time, number, range, etc), native audio/video support, SVG, and MathML. It also defined several powerful APIs for features like offline web apps, web workers, websockets, geolocation, and local storage.

HTML Syntax

Let‘s dive deeper into the syntax rules of HTML. An HTML element consists of:

  • An opening tag like <p>
  • Some content inside the tag
  • A closing tag like </p>

Some elements, called void elements, don‘t require a closing tag. Examples include <img>, <br>, <hr>, and <input>.

Elements can also have attributes inside the opening tag to provide additional information. Attributes consist of a name and a value, separated by an equals sign. For example:

<a href="">Link to Example</a>

Here, href is the attribute name and is the attribute value.

There are many global attributes that can be applied to any HTML element, like:

  • class – specifies one or more class names for an element, used for styling and scripting
  • id – specifies a unique id for an element, also used for styling and scripting
  • title – specifies extra information about an element, displayed as a tooltip on hover
  • style – specifies inline CSS styles for an element
  • lang – specifies the language of the element‘s content
  • hidden – indicates that the element is not yet relevant, so the browser won‘t render it

Additionally, many elements have their own specific attributes. For example, the <img> element has src to specify the image URL and alt for the alternate text. The <a> element has href for the link destination and target to control where the link opens.

HTML is not case-sensitive for tag and attribute names (although lowercase is recommended). However, it is case-sensitive for attribute values in certain circumstances (e.g. class and id names).

Proper HTML syntax and usage is important not only for valid code, but for accessibility. Assistive technologies like screen readers rely on the correct usage of semantic HTML tags to help users navigate and understand content. Some key accessibility considerations are:

  • Using heading tags (<h1> to <h6>) to convey the content hierarchy
  • Providing text alternatives for images and media with alt attributes
  • Using semantic tags like <header>, <nav>, <main>, <article>, <section> instead of generic <div> tags
  • Ensuring sufficient color contrast between text and background
  • Enabling keyboard navigation with proper focus order and tab stops

By writing accessible HTML, you ensure that your content can be used by the widest possible audience, regardless of ability.

Relationship with CSS and JavaScript

While HTML provides the content and structure of a web page, CSS (Cascading Style Sheets) and JavaScript add style and interactivity.

CSS is a stylesheet language that lets you control the visual appearance of HTML elements, like colors, fonts, spacing, sizing, and layout. CSS can be embedded inside HTML using the <style> tag, or linked from an external .css file using the <link> tag.

Here‘s an example of some CSS to style an HTML button:

button {
  background-color: #4285F4;
  color: white;
  border: none;
  padding: 12px 24px;
  font-size: 16px;
  cursor: pointer;

button:hover {
  background-color: #3367D6;

This CSS selects all <button> elements and applies several style rules:

  • Sets the background color to a blue shade
  • Sets the text color to white
  • Removes the default button border
  • Adds padding around the button text
  • Sets the font size to 16 pixels
  • Changes the mouse cursor to a hand pointer on hover
  • Changes the background to a darker blue on hover

JavaScript is a scripting language that enables dynamic behavior and interactivity in web pages. It can manipulate the HTML DOM to change content, respond to events, fetch data from APIs, and much more.

Here‘s a simple example of some JavaScript to show an alert when a button is clicked:

<button id="myButton">Click me!</button>

const button = document.getElementById(‘myButton‘);
button.addEventListener(‘click‘, function() {
  alert(‘Hello, world!‘);

This code first selects the button element by its id attribute using getElementById. Then it attaches a click event listener to the button using addEventListener. When the button is clicked, the function passed to the listener will be called, showing the "Hello, world!" alert.

Together, the combination of HTML, CSS, and JavaScript is incredibly powerful for building interactive, data-driven web applications.

HTML in Modern Web Development

In recent years, the web development landscape has evolved rapidly with the rise of front-end libraries, frameworks, and build tools. However, HTML remains as relevant as ever in modern web development.

Popular front-end frameworks like React, Angular, and Vue all ultimately compile down to HTML, CSS, and JavaScript for the browser to render. Having a solid grasp of HTML fundamentals makes it easier to understand how these frameworks structure and manipulate content under the hood.

Another significant trend is the JAMstack (JavaScript, APIs, Markup) architecture for building websites. JAMstack sites are characterized by using static site generators to pre-render HTML pages at build time, coupled with client-side JavaScript and reusable APIs for dynamic functionality. This approach can offer better performance, security, and scalability over traditional server-rendered pages.

Some popular static site generators that leverage HTML and templating languages include:

  • Gatsby (React-based)
  • Next.js (React-based)
  • Hugo (Go-based)
  • Jekyll (Ruby-based)
  • Eleventy (Node.js-based)

These tools allow developers to write modular, component-based HTML that gets transformed into optimized static assets.

From a career perspective, HTML skills are in high demand. According to the 2020 Stack Overflow Developer Survey, HTML/CSS was the #3 most popular technology, used by 63.1% of professional developers. The U.S. Bureau of Labor Statistics predicts 8% job growth for web developers and digital designers between 2019-2029, much higher than the 4% average for all occupations.

Clearly, HTML expertise remains a valuable asset in the modern web development job market.


In summary, HTML is a crucial building block of the web that every developer should master. Its declarative syntax for structuring semantic content is surprisingly powerful and versatile.

Over 30 years since its invention, HTML has constantly evolved to meet the changing needs of the web. Today it offers a rich set of tags, attributes, and APIs for building accessible, interactive, and performant websites and apps.

Combined with CSS for styling, JavaScript for interactivity, and static site generators for fast builds, HTML fits naturally into the modern web development ecosystem.

Some best practices to follow when writing HTML are:

  • Always use a <!DOCTYPE html> to specify the HTML version
  • Structure content semantically with appropriate tags like headings, sections, articles, etc
  • Provide text alternatives for images and media
  • Ensure code is valid and free of syntax errors
  • Indent nested tags consistently for readability
  • Optimize for accessible, responsive design across devices

By learning and applying HTML effectively, you‘ll be well on your way to becoming a proficient web developer. As the most fundamental web language, HTML skills are in demand and will remain relevant for the foreseeable future.