Deciphering CSS: definition and crucial role in web development

by our Web Agency Optimize 360

CSS stands for Cascading Style Sheets. cascading style sheetis an essential computer language for creating attractive and dynamic web pages.

In this article, we're going to explore what CSS is, how it works, the basics of using it, and its central place in the world of web design. web development.

What is CSS?

CSS is a computer language used to describe the presentation of documents. HTML (Hypertext Markup Language) or XML (Extensible Markup Language).

Designed by Håkon Wium Lie in 1996, its main purpose is to control the layout of a web page by modifying its overall appearance: layout, fonts, colours, etc.

To put it simply, if we think of a web page as a house, HTML would be the cement and bricks that form its structure, while the CSS act like paint, wallpaper and other decorative elements so it can be customised to suit individual tastes.

How CSS works

CSS works by a series of rules and selectors applied to the HTML tags in your document. Rules are written between braces and define a set of properties and values that will be applied to the corresponding content. Selectors are used to target the HTML elements to which these rules are applied.

CSS selectors

There are several types of CSS selector. Here are some of the most commonly used:

• • Element selector : targets all elements of a certain type (for example, all <p>).
  • Class selector : targets all elements with a certain class assigned (for example, all tags with the class= "example" attribute).
  • ID selector : targets a single element with a certain assigned identifier (for example, the only tag with the id="example" attribute).
  • Down selectort: targets elements that are descendants of another specific element (for example, all
  • tags located inside an
    tag).

  Example of a CSS rule

  Here is a simple example of a CSS rule:

  p { font-family : Arial, sans-serif; font-size : 14px; color : red; }

  In this example, the selector is "p", which means that it targets all the paragraphs on the page. The properties and values between the braces are then applied to all the paragraphs: an Arial font, size 14px, colour red.

  Integrating CSS into a web page

  There are several ways of integrating CSS into a web page. Here are the three main ones:

  1. Internal CSS : direct integration of style sheets in the section of the HTML file using tags.
  2. External CSS : create a separate file with the ".css" extension containing all the rules, then import via a link placed in the section of the HTML file.
  3. CSS online : adding styles directly to HTML tags via the "style" attribute. This method is generally not recommended, as it makes the code more difficult to read and maintain.

  As a general rule, it's best to use external CSS files to clearly organise and separate your code, improve the maintenance and allow resources to be loaded in parallel, which optimises page loading time.

  The importance of CSS in web development

  CSS plays an essential role in the creation of modern, harmonious and adaptable websites. It has many advantages:

  • It facilitates visual consistency across an entire site by grouping together all the formatting
  • It enables save time avoiding code repetition and simplifying maintenance
  • It encouragesaccessibilityfor people with special display needs (contrast, font size, etc.).
  • It facilitates the implementation of responsive designsThey are adapted to different types of screen (computers, smartphones, tablets, etc.).

  So mastering CSS is essential not only to bring attractive designs to life, but also to optimise the browsing experience for visitors to your site.

  Creating a website with HTML, CSS and JavaScript

  Although CSS is essential for controlling the layout of web pages, it is only part of the arsenal needed for web development. To create a website functional and interactive, it is also important to know :

  • HTML : markup language used to structure content (text, images, links, etc.).
  • JavaScript : programming language used to add dynamic and interactive features to web pages (animations, forms, visual effects, etc.).

  These three pillars - HTML, CSS and JavaScript - form the basis of what is known as "front-end development" and are essential for anyone wishing to design modern, attractive websites.