Cascading Stylesheets — or CSS — is the first technology you should start learning after HTML. While HTML is used to define the structure and semantics of your content, CSS is used to style it and lay it out. For example, you can use CSS to alter the font, color, size, and spacing of your content, split it into multiple columns, or add animations and other decorative features.

You should learn the basics of HTML before attempting any CSS. We recommend that you work through our Introduction to HTML module first. In that module, you will lear about:

• HTML basics
• More advanced HTML modules
• CSS, starting with the introduction to CSS module
• CSS basics
• JavaScript Basics
• JavaScript, and how to use it to add dynamic functionality to the web page

Once you understand the fundamentals of HTML, we recommend that you learn further HTML and CSS at the same time, moving back and forth between the two topics. This is because HTML is far more interesting and much more fun to learn when you apply CSS, and you can't really learn CSS without knowing HTML.

Before starting this topic, you should also be familiar with using computers and using the web passively (i.e., just looking at it, consuming the content). You should have a basic work environment set up as detailed in Installing basic software and understand how to create and manage files, as detailed in Dealing with files — both of which are parts of our Getting started with the web complete beginner's module.

This topic contains the following modules, in a suggested order for working through them. You should definitely start with the first one.

CSS first steps

CSS (Cascading Style Sheets) is used to style and lay out web pages — for example, to alter the font, color, size, and spacing of your content, split it into multiple columns, or add animations and other decorative features. This module provides a gentle beginning to your path towards CSS mastery with the basics of how it works, what the syntax looks like, and how you can start using it to add styling to HTML.

CSS building blocks

This module carries on where CSS first steps left off — now you've gained familiarity with the language and its syntax, and got some basic experience with using it, its time to dive a bit deeper. This module looks at the cascade and inheritance, all the selector types we have available, units, sizing, styling backgrounds and borders, debugging, and lots more. The aim here is to provide you with a toolkit for writing competent CSS and help you understand all the essential theory, before moving on to more specific disciplines like text styling and CSS layout.

Styling text

With the basics of the CSS language covered, the next CSS topic for you to concentrate on is styling text — one of the most common things you'll do with CSS. Here we look at text styling fundamentals, including setting font, boldness, italics, line and letter spacing, drop shadows and other text features. We round off the module by looking at applying custom fonts to your page, and styling lists and links.

CSS layout

At this point we've already looked at CSS fundamentals, how to style text, and how to style and manipulate the boxes that your content sits inside. Now it's time to look at how to place your boxes in the right place in relation to the viewport, and one another. We have covered the necessary prerequisites so we can now dive deep into CSS layout, looking at different display settings, modern layout tools like flexbox, CSS grid, and positioning, and some of the legacy techniques you might still want to know about.

Use CSS to solve common problems provides links to sections of content explaining how to use CSS to solve very common problems when creating a web page.

From the beginning, you'll primarily apply colors to HTML elements and their backgrounds; change the size, shape, and position of elements; and add and define borders on elements. But there's not much you can't do once you have a solid understanding of even the basics of CSS. One of the best things about learning CSS is that once you know the fundamentals, usually you have a pretty good feel for what can and can't be done, even if you don't actually know how to do it yet!

CSS (Cascading Style Sheets) allows you to create great-looking web pages, but how does it work under the hood? This article explains what CSS is, with a simple syntax example, and also covers some key terms about the language.

As we have mentioned before, CSS is a language for specifying how documents are presented to users — how they are styled, laid out, etc.

A document is usually a text file structured using a markup language — HTML is the most common markup language, but you may also come across other markup languages such as SVG or XML.

Presenting a document to a user means converting it into a form usable by your audience. Browsers, like Firefox, Chrome, or Edge , are designed to present documents visually, for example, on a computer screen, projector or printer.

CSS can be used for very basic document text styling — for example changing the color and size of headings and links. It can be used to create layout — for example turning a single column of text into a layout with a main content area and a sidebar for related information. It can even be used for effects such as animation. Have a look at the links in this paragraph for specific examples.

CSS is a rule-based language — you define rules specifying groups of styles that should be applied to particular elements or groups of elements on your web page. For example "I want the main heading on my page to be shown as large red text."

The following code shows a very simple CSS rule that would achieve the styling described above:

           
        h1   {  
               color:  red;
               font-size:  5em;
        }    
        
    

The rule opens with a selector . This selects the HTML element that we are going to style. In this case we are styling level one headings (< h1 >).

We then have a set of curly braces { }. Inside those will be one or more declarations, which take the form of property and value pairs. Each pair specifies a property of the element(s) we are selecting, then a value that we'd like to give the property.

Before the colon, we have the property, and after the colon, the value. CSS properties have different allowable values, depending on which property is being specified. In our example, we have the color property, which can take various color values. We also have the font-size property. This property can take various size units as a value.

A CSS stylesheet will contain many such rules, written one after the other.

           
        h1   {  
               color:  red;
               font-size:  5em;
        }    
        
        
           
        p   {  
               color:  black;
        }    
        
    

You will find that you quickly learn some values, whereas others you will need to look up. The individual property pages on MDN give you a quick way to look up properties and their values when you forget, or want to know what else you can use as a value.

The main entry point for CSS documentation on MDN, where you'll find detailed reference documentation for all features of the CSS language. Want to know all the values a property can take? This is a good place to go.

Use this CSS reference to browse an alphabetical index of all of the standard CSS properties, pseudo-classes, pseudo-elements, data types, functional notations and at-rules. You can also browse key CSS concepts and a list of selectors organized by type. Also included is a brief DOM-CSS / CSSOM reference.

Basic rule syntax

Style rule syntax

          
       style-rule ::= 
               selectors-list  {
                    properties-list
            }
        
    

... where :

          
       selectors-list ::= 
               selector[ :pseudo-class ]  [ ::pseudo-element ]
               [,  selectors-list]
        
        
           
       properties-list ::= 
               [ property :  value ]  [ ; properties-list ]
        
    

The syntax for each specified value depends on the data type defined for each specified property.

Style rule examples

           
        strong   {  
               color:  red;
        
        
           
        div.menu-bar li:hover > ul   {  
               display:  block;
        }    
        
    

For a beginner-level introduction to the syntax of selectors, see our guide on CSS Selectors. Be aware that any syntax error in a rule definition invalidates the entire rule. Invalid rules are ignored by the browser. Note that CSS rule definitions are entirely (ASCII) text-based, whereas DOM-CSS / CSSOM (the rule management system) is object-based.

CSS on MDN

The main entry point for CSS documentation on MDN, where you'll find detailed reference documentation for all features of the CSS language. Want to know all the values a property can take? This is a good place to go.