How HTML, CSS and JavaScript work together in web pages

The three main technologies used to create web pages (HTML, CSS and JavaScript) each do different special jobs.

  • HTML should be used only for structuring content.
  • Cascading Style Sheets should be used for applying all visual styles.
  • JavaScript should be used for (almost) all interactive functionality, and should always be referenced in separate files, never written into HTML.

How HTML, CSS and JS work together

The web page you see in your browser may be a combination of structure, style and interactivity. These jobs are undertaken by 3 different technologies, HTML, Javascript, and CSS which your browser knows how to interpret.

A web page may combine structure from HTML, style from CSS and functionality from JavaScript
HTML
marks the content up into different structural types, like paragraphs, blocks, lists, images, tables, forms, comments etc.
CSS
tells the browser how each type of element should be displayed, which may vary for different media (like screen, print or handheld device)
JavaScript
tells the browser how to change the web page in response to events that happen (like clicking on something, or changing the value in a form input)

New eBookNew eBook - Guide to Semantic HTML

Ben Hunt adds another great eBook to the collection with his "Guide to Semantic HTML". The book gives you advice and tips on how, and why to use semantic HTML.

Included is a comprehensive list of HTML tags, each with their semantically appropriate uses, along with a worked example taking you through the process of how to build a website using semantic HTML.

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New eBookNew eBook - Web page production with xHTML and CSS #1

Experience the thought process of a professional web producer as he guides you through the web page production process, from photoshop design to working HTML template.

The book tells you how to approach web production, beginning with semantic HTML, guiding you through how to slice up a photoshop document, and finally how to use CSS for presentation.

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The 2 most important things to learn about web page production are:

  1. Use the correct HTML tags that mean what they say.
  2. Keep your HTML, CSS and JavaScript code separate.

1. Use HTML properly

Different HTML tags describe the structure of content. Each one has its own meaning, and you should only ever use each one in accordance with its meaning, and in its proper place.

When people talk about "semantic" HTML, this is what they mean.

In the HTML section, I'll explain what each tag means, and where it's OK to use it.

2. Keep 'em separate

This simply means: Don't put JavaScript or CSS in your HTML. Put them in separate files, called in by your HTML pages.

There are lots of good reasons for this, the main ones being:

  • It's more logical and simpler. And simple is good.
  • Easier management: Keeping all your styles and functional code in one place makes it quicker, easier and safer to change in future.
  • Easier re-purposing: It's easier to design your web site to look or work differently on different user agents (e.g. handheld browsers, audio browsers, or TV)
Scratchmedia, web application user interface design

Scratchmedia specialises in designing new Web2.0 user interfaces. We also provide expert reviews and consulting services.

 

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