What is CSS (Cascading Styles) – a complete guide

Everything you need to know about CSS (Cascading Styles) – what it is, what it’s for, how to format your website using CSS.

What is CSS

CSS stands for Cascading Style Sheet. In translation, it means Cascading Style Sheets. CSS is a simple mechanism for visually formatting Internet documents.

When you apply CSS to an HTML document, you can modify elements such as font, color, and spacing. This allows you to maintain a consistent look across multiple pages of a website. CSS separates content from design, ensuring that websites are accessible and styled effectively, improving the user experience.

Before studying CSS, I recommend first looking at this complete HTML tutorial .

History of CSS

The birth of CSS, formally known as Cascading Style Sheets , dates back to 1996, when the W3C (World Wide Web Consortium) released CSS1 . The introduction of CSS revolutionized web design by providing a new, more efficient method of styling web pages. Since then, CSS has evolved in several versions. CSS2.1 , which came after CSS1, introduced features like fixed positioning and z-index. The latest evolution, CSS3 , split the specification into modules and introduced new features such as animations, flexbox for layout, and media queries for responsive design.

Once you understand what CSS is and its historical context, you’ll be better prepared to use its full potential in web development.

CSS is used everywhere

This language is used to visually stylize most sites on the Internet. For example, CSS is used to define a page’s layout, color, and overall page style. You can use CSS to set fonts, images, page backgrounds, page layouts, and more.

In WordPress , CSS uses individual themes . It determines their layout, overall design and style.

CSS Basics

Understanding the basics of CSS includes learning its syntax and structure, and how to use selectors and properties to style web elements.

Syntax and structure

CSS consists of a series of rules that define how HTML elements are displayed. These rules consist of selectors and declarations. The declaration itself consists of properties and their corresponding values, which are structured as follows:

selektor {
   vlastnosť: hodnota;
}

Selectors are the names assigned to the elements on the web page that you want to modify. Statements are enclosed in curly brackets{} and declare how you want to style the selected elements.

Selectors and properties

There are different types of selectors :

• Element selectors that select HTML elements based on tag name.
• Class selectors that select elements based on an attributeclass . Their prefix is. (dot).
• ID selectors that select a unique element based on its attributeid with a prefix# (hash symbol).

Each selector can be followed by one or more declarations , which are property-value pairs separated by a colon and terminated by a semicolon.

Properties are aspects of HTML elements that you want to modify, such ascolor ,font-size ,margin ,padding etc. A rule represents the entire statement, including a selector and a block of declarations.

.trieda {
   color: blue;
   font-size: 14px;
}

Each property is followed by a value that specifies how the property should be applied to the element. Each property-value pair is a declaration .

After understanding the basics of syntax, selectors, and CSS properties, you can begin styling web page elements to create visually impressive web content.

CSS integration

Integrating CSS into HTML helps you control the presentation of your website. Whether you prefer to keep styles close to tags, balance accessibility and maintainability, or keep things separate entirely, CSS offers you a variety of methods for using styles.

Inline CSS

Inline CSS is when you apply a style directly in your HTML tags using an attributestyle . This method is generally used to apply unique styles to a single HTML element. Here is an example:

<p style="color: blue;">Tento text je modrý.</p>

Using inline CSS affects the maintainability of your HTML documents because the styles are not centralized, making it difficult to manage when there are multiple instances of the same style.

Internal CSS

Internal CSS styling is defined in<head> of the HTML document within the tags<style> . This is a viable option when you are working with a single HTML document and want to apply styles that are unique to that page.

<head>
<style>
  body {
    background-color: lightgrey;
  }
</style>
</head>

You don’t need any additional files and styles are applied consistently across the page, but as with inline CSS, internal styling doesn’t support reuse across multiple pages.

External CSS

Use external CSS to link to a separate file.css from an HTML document that can control styles for multiple pages on a site. This method is achieved using a tag<link> in the section<head> :

<head>
<link rel="stylesheet" href="styles.css">
</head>

Your styles are contained in a single file with the extension.css , which facilitates adjustment and maintenance. You write your CSS in a text editor and upload the stylesheet along with the HTML files. This is the most efficient method of editing multiple HTML documents with a consistent design.

Editing text style

In CSS, you have the ability to control the visual aspects of text, from font family to letter spacing. You use properties to define how your text should appear on your website, ensuring readability and aesthetic appeal.

Fonts and typography

Consider both aesthetics and readability when choosing fonts for your website. Font family specifies the font type, which can be a specific name, such as “Arial,” or a general group, such as “serif.” The font-size property adjusts the size of your text and is usually defined in pixels, em, or rem.

An example of using a font family:

p {
  font-family: Arial, sans-serif;
}

Example of using the font size:

h1 {
  font-size: 32px;
}

Text properties and effects

Different properties affect other aspects of the text:

• Color : determines the color of the text. You can use named colors, hexadecimal, RGB or HSL values.
• Letter Spacing : increases or decreases the space between characters, usually measured in pixels or em.

Remember to keep text properties consistent to create a cohesive look for your website.

CSS Box Model

The CSS Box Model is a fundamental concept that determines how elements are rendered on a web page. It defines the structure and layout of each HTML element as a rectangular box that contains borders, margins, padding, and the actual content.

Margins and outlines

In the box model, borders include content and padding, acting as an intermediary between padding and margins. Whenever you set the width of a border with CSS, you define the thickness of that border. Propertyborder can be divided into subproperties for each side (border-top ,border-right ,border-bottom ,border-left ), allowing you to customize each one individually. You can also define a style (solid ,dotted ,dashed etc.) and the border color.outline it is similar to a border, but does not take up space in the box model – it is drawn outside the element’s frame and does not affect the element’s position.

Margins and indentation

Borders are the outer layer of the box model and create space between the edge of one box and another. They collapse when they meet; a larger border size is used when adjacent fields have borders. The edges are transparent and have the following properties:margin-top ,margin-right ,margin-bottom ,margin-left code> .

The padding is located directly inside the borders, surrounding the actual content, and its primary function is to create space within the frame, between the content and the border. Unlike borders, it is possible to define a fill color that matches your design because it is part of the element’s box. It also has individual properties for each side (padding-top ,padding-right ,padding-bottom apadding-left ).

Remember that CSS propertieswidth aheight refer to the size of the content. If you include margins and padding, they increase the overall size of the field unless you use the propertybox-sizing set to a valueborder-box , which resizes the content to include padding and margins within the declared width and height.

Visual formatting

In CSS, visual formatting is a key aspect that determines how elements appear on a web page. Your understanding of its principles affects everything from layout to composition context.

Background and colors

CSS allows you to set the background color and background image of elements. Features likebackground-color you use to specify a solid color, whilebackground-image allows you to place an image behind the content. Propertybackground combines these settings along with other settings such asbackground-position abackground-repeat , giving you fine-grained control over the element’s background visuals.

Positioning and Z-index

It uses a CSS property to control the layout of elements position with values ​​like static, relative, absolute, fixed a sticky. Propertyz-index works in conjunction with positioning to determine stack order of elements; higherz-index means the element will be closer to the top of the composition context. Remember thatz-index it only affects elements that have a valueposition other thanstatic .

Flexbox and CSS Grid

Flexbox and CSS Grid are powerful layout models that offer different approaches to creating responsive designs. Flexbox works on a one-dimensional axis, row or column, making it ideal for linear layouts. Use properties like to manipulate the layoutdisplay: flex and other child properties such asflex-grow aflex-shrink .

CSS Grid, on the other hand, works on a two-dimensional grid system that is controlled by properties likedisplay: grid . You definegrid-template-columns agrid-template-rows to create a framework for your content. CSS Grid easily allows for complex layouts, allowing you to place elements in precise locations within the grid structure.

Advanced design techniques

In this section, you’ll learn how to improve the visual appeal and interactivity of your web pages using CSS. Mastering these techniques will allow you to create dynamic, responsive designs that grab the user’s attention.

Transforms and transitions

Transforms allow you to rotate , scale , tilt , and translate elements to change how they are rendered on a web page. When you apply a transform, the change is instantaneous, but you can control the timing by combining it with transitions .

• Turn : transform: rotate(45deg);
• Scale : transform: scale(1.5);
• Translate : transform: translate(30px, 50px);
• Chamfer : transform: skew(20deg, 15deg);

Transitions allow for smooth changes between states. When you specify a transition, you must define which property is passed, the duration, the timing function, and any delay.

transition: background-color 0.5s ease-in-out 0s;

By tweaking these parameters, you’ll create a smooth, natural motion that adds sophistication to your page.

Animations

CSS animations take interactivity to the next level by defining a sequence of styles that an element will cycle through. To create an animation, you must first specify Keyframes , which outline the start and end points of the animation, as well as any intermediate steps:

@keyframes slidein {
   from { transform: translateX(0%); }
   to { transform: translateX(100%); }
}

To activate the animation, apply it to the element and define its duration and timing function and number of iterations:

prvok {
    animation: slidein 3s easy-in-out infinite;
}

Animations can loop endlessly or play a set number of times, giving you precise control over how elements interact with users on your site. These advanced design techniques will make your website stand out with a professional, polished look and engaging user experience.

Responsive web design

Responsive web design (RWD) ensures that your website looks good and works well on different devices. It focuses on providing a smooth experience on different screen sizes using variable grids, flexible images and Media Queries.

Media Queries

Media Queries are the cornerstone of responsive web design. They allow you to apply CSS styles based on device screen size, orientation, and resolution. For example, you can write a media query to change the page layout when the display area is less than 768 pixels wide:

@media (max-width: 768px) {
  .container {
    width: 100%;
  }
}

This code ensures that the class.container will take up the entire width of the screen on devices with a display area wider than 768 pixels.

Responsive units

In responsive design, it’s important to use units that allow your layout to adapt to the user’s environment.

Pixels ( px ) are absolute units and do not scale to screen size, which can lead to a poor user experience on mobile devices.

Instead, use relative units such as percentages ( % ), viewport width ( vw ), and viewport height ( vh ). For example, resizing elements by percentage can cause the content to change proportionally to the display area:

.content {
   width: 80%;
}

This makes it wonderful.content 80% wider than its parent, allowing for a fluid layout that adapts to different devices.

Frameworks and preprocessors

On your journey to creating stylish, responsive web designs, you’ll find that CSS frameworks and preprocessors are powerful tools that increase the efficiency and maintainability of your code. Use these tools to streamline your workflow and apply sophisticated styles with less effort.

Popular CSS frameworks

Bootstrap : As one of the most widely used CSS frameworks, Bootstrap provides you with a comprehensive set of pre-made style sheets. You get a responsive grid system, pre-designed components and JavaScript plugins that will significantly speed up the development process.

Foundation : This is a sophisticated enterprise-level framework designed for modularity and flexibility. Foundation offers you a modular approach with different templates to help you easily create complex layouts and responsive designs.

Tailwind CSS : Unlike traditional frameworks, Tailwind CSS works on a utility-first principle, offering you atomic classes to create your own designs without leaving HTML.

Use of preprocessors

SASS : This preprocessor extends CSS with features such as variables, nested rules, and mixins. With SASS, you can write more organized and maintainable style sheets that are then compiled into standard CSS.

LESS : Like SASS, LESS enhances CSS with variables, mixins, and functions, allowing you to create more dynamic and effective styles. It also compiles to CSS for cross-browser compatibility.

Stylus : Offering great flexibility and expressive syntax, Stylus is a preprocessor that can run both synchronously and asynchronously to suit a wide range of project requirements.

With CSS frameworks, you can take advantage of ready-to-use components and grid systems, while preprocessors allow you to write CSS in a programming construct that is eventually compiled into browser-understandable code.

CSS Best Practices

Using best practices when working with CSS ensures that your stylesheets are not only efficient, but also maintainable and scalable. Keep these concepts in mind to increase the performance and coherence of your projects.

Writing CSS efficiently

Selectors and specificity:

• Use class selectors to achieve low specificity and easier overrides.
• Avoid overly specific selectors to reduce complexity and improve performance.

Performance Optimization:

• Minimize the use of expensive properties such asbox-shadow afilter , which can cause redrawing and reformatting.
• Implement lazy loading for off -screen images usingloading="lazy" , to save bandwidth and increase page speed.

CSS architecture and methodologies

Organizational strategies:

• Adopt a methodology such as BEM (Block Element Modifier) ​​to achieve consistent naming conventions.
• Structure your CSS using a clear hierarchy, while for larger projects consider SMACSS (Scalable and Modular Architecture for CSS) .

Scalability and maintainability:

• Using CSS preprocessors like Sass, you can take advantage of variables, mixins, and functions for more dynamic stylesheets.
• Consider modular CSS architectures such as OOCSS (Object-Oriented CSS) to encourage reuse and reduce redundancy.

By following these steps, you’ll create CSS styling that not only works well, but adapts to your project while remaining easy to maintain.

Working with CSS

Understanding how to work with CSS involves more than just writing style rules; it also requires rigorous testing and ensuring consistency of styles across browsers.

Debugging and testing

When you encounter a problem with CSS, the first step is to use the developer tools in your web browser. These tools allow you to review and edit HTML and CSS in real time. For a simplified debugging process:

1. Check the element that is not displaying correctly.
2. Check the CSS properties applied to it.
3. Adjust properties and monitor changes in the browser to identify problematic code.

For testing , it is essential to check the CSS on different web pages and elements within your website to ensure consistency. Automated testing tools can simulate a wide variety of scenarios by applying your CSS to different HTML structures to catch inconsistencies or unexpected behavior.

Browser compatibility and substitutes

Browser support for CSS features varies and it is your responsibility to ensure that your website renders correctly in all major browsers. Browser compatibility solution:

• Use resources like caniuse.com to check the compatibility of CSS properties
• Implement fallbacks for older browsers. For example, if you use a modern layout feature like CSS grid, for browsers that don’t support grid, provide a fallback to a more traditional layout technique like float or display: table.

For features that degrade gracefully, consider using s feature queries@supports , to apply the style only when the browser supports a particular property or value. This ensures that your website remains functional and visually appealing even if the user’s browser doesn’t render all of the style tweaks.

CSS and accessibility

When approaching web design, incorporating accessibility principles into your CSS is key. Remember that while CSS primarily controls visual presentation, it can also affect the accessibility of content to users with disabilities.

Semantic markup: Always pair CSS with semantic HTML. Use HTML elements that convey meaning about the type of content they encapsulate, such as<header> for section header or<nav> for navigation links. This ensures that the content remains understandable after the styles are removed.

• Visual design:
  • Colors: Ensure sufficient contrast between text and background colors. Do not use color as the only method of conveying information.
  • Text: Use relative units (such as em or rem) to adjust the size of text so that users can resize the text according to their needs.

AR and ARIA: Accessible Rich Internet Applications (ARIA) attributes can complement HTML to improve accessibility when creating complex web components. For examplerole="button" makes an element that is not a native button element available as an assistive technology button.

• CSS Techniques:
  • Correctly hide elements usingvisibility:hidden ordisplay:none , so that they are also hidden from screen readers.
  • Use stylesfocus for interactive elements to provide clear keyboard navigation instructions.

CSS	Impact on availability
color	It must have a high contrast with the background for legibility
font-size	Use relative units to zoom in/out
display/visibility	Use them to hide elements to improve readability

By using these practices in your CSS, you’ll improve the accessibility of your web content, making it more inclusive and user-friendly for everyone.

CSS specifications and documentation

Your ability to use CSS styling effectively depends on a thorough understanding of its specifications and documentation. The guidelines and references outlined by the W3C are critical to mastering web design.

W3C specifications

The World Wide Web Consortium (W3C) is responsible for developing CSS specifications. You will find that these specifications cover a wide range of information, from basic structure to advanced features.

CSS specifications are designed to inform you about how to properly implement various aspects of CSS in web documents.

For example, Media Queries extend the capabilities of @media rules by adding parameters to accommodate display size, color depth, and aspect ratio variations. The CSS Working Group plays a key role in developing these standards, ensuring they are comprehensive and up-to-date.

CSS links and resources

Various online platforms provide practical CSS references and resources . The MDN Web Docs stand out as a valuable resource and offer comprehensive documentation on CSS. Here you will find detailed information about:

• CSS Syntax : Understanding the proper format for writing CSS, including selectors, pseudo-classes, pseudo-elements, properties, and values.
• Examples of style rules : Practical application of CSS rules to set styles in web documents.

Use these resources to deepen your knowledge and improve the implementation of CSS in various media and platforms. Remember that cascading is a fundamental concept of CSS, where the order of CSS rules and their specificity determine how styles are applied to HTML elements.

Learning CSS

Once you start learning CSS, you’ll find plenty of resources and methods to improve your web development skills. It is important to start with comprehensive tutorials and then apply your knowledge by working on practical exercises and projects.

CSS tutorials and guides

Start your journey with CSS tutorials that provide step-by-step instructions and clear examples . Platforms like W3Schools offer interactive tutorials where you can immediately try it yourself by editing the CSS and viewing the results in their online editor. Each chapter usually includes examples to help reinforce concepts.

Similarly, MDN Web Docs is a trusted resource for teaching web technologies, including CSS. Their CSS tutorials cover the basics from HTML styling, box model, selectors to more advanced topics like animations and layout techniques.

CSS exercises and projects

After learning the basics through tutorials, it’s important to gain hands-on experience. Find CSS exercises and create small projects to apply what you’ve learned.

You can start with simple tasks like styling a paragraph or designing a navigation bar, then scale up to create multi-column layouts or even an entire website.

To test your CSS knowledge:

1. Create a simple HTML page.
2. Customize your style using a CSS file linked to HTML.
3. Experiment with different CSS properties to see their effects.

Here’s a basic exercise for editing paragraph text:

<!-- Index.html -->
<!DOCTYPE html>
<html>
<head>
<link href="styles/style.css" rel="stylesheet" />
</head>
<body>
<p>Hello, World!</p>
</body>
</html>

/* styles/style.css */
p {
  color: red;
}

By completing these hands-on projects, you’ll reinforce your learning and gradually build a portfolio to showcase your growing expertise in CSS.