What Is a Cascading Style Sheet?

We go into details about cascading in Chapter  15, “Cascading and
inheritance.” Before that, there is much to learn about fonts,
space and ­colors. Now you have the basics of how to create CSS rules and style sheets. In order for the style sheet to have any effect you have to “glue” your style sheet to your HTML document.

The CSS border property defines a border
around an HTML element. An external style sheet is used to define the style for many HTML pages. At this point we’ve already looked at CSS fundamentals, how to style text, and how to style and web development css cascading 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 to each other. The style definitions are normally saved in external .css files.

Anatomy of a rule

Each rule or rule-set consists of one or more selectors, and a declaration block. CSS is used to define styles for your web pages, including the design, layout
and variations in display for different devices and screen sizes. This CSS media query applies styles to elements with the class “column” when the screen width is 600 pixels or less, making the layout responsive to different screen sizes. CSS (Cascading Style Sheets) is used to style and layout 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. Notice that the padding property was only given one value (0.5em).

However, the user can say that a rule is
very import­ant and it will then override any author or browser
styles. User-agents, or browsers, have basic style sheets that give default styles to any document. Most browsers use actual stylesheets for this purpose, while others simulate them in code.

Link to External CSS

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. As a general rule, properties in CSS inherit from
parent to child elements as described in the previous examples. Some properties, however, don’t inherit and there is always a good
reason why. We will use the background property (described in Chapter 11) as an
example of a property that doesn’t inherit.

CSS, or Cascading Style Sheets, offers a flexible way to style web content, with styles originating from browser defaults, user preferences, or web designers. These styles can be applied inline, within an HTML document, or through external .css files for broader consistency. Not only does this simplify web development by promoting reusability and maintainability, it also improves site performance because styles can be offloaded into dedicated .css files that browsers can cache. Before CSS, nearly all presentational attributes of HTML documents were contained within the HTML markup. All font colors, background styles, element alignments, borders, and sizes had to be explicitly described, often repeatedly, within the HTML.

Further reading

A class may apply to any number of instances of any element. The name cascading comes from the specified priority scheme to determine which declaration applies if more than one declaration of a property match a particular element. The CSS layout cookbook aims to bring together recipes for common layout patterns, things you might need to implement in your sites.

Using Cascading Style Sheets (CSS) allows developers to separate content from presentation. In other words, with CSS the visual layout of a Web page can be established with style sheets, while the content can be put into HTML. CSS gives developers the ability to change the linear layout of a page — the order of elements on a Web page when all styles and formatting are removed — without altering its visual layout. This is important because the linear reading order of Web content is the order in which screen readers access the content. Another advantage with CSS is that it gives the end user control over the Web page style as well. For example, the user can change the background color or increase the font.

Is CSS a programming language?

We have known for years that designers want to develop their
own style sheets. However, we discovered that users, too, want the
option of influencing the presentation of their documents. With
CSS, they can do this by supplying a personal style sheet that
will be merged with the browser’s and the designer’s style sheets. Any conflicts between the various style sheets are resolved by the
browser. Usually, the designer’s style sheet will have the
strongest claim on the document, followed by the user’s, and then
the browser’s default.

Classes are described in What Are Cascading Style Sheet Rules and Classes?. CSS is a critical tool for web designers and is widely supported by all modern web browsers. Please note, though, that the use of CSS does not in itself make a Web page accessible. The most critical consideration is the use of valid, semantic (X)HTML. In fact, any page that uses styles should be usable with the styles disabled.

CSS (Cascading Style Sheets)

The ­second rule only affects h1 elements in the document and is therefore more
specific. In the example, it is “green,” but it could just as easily be blue, red, yellow, or some other color. The only thing creating this visual change is the use of a different CSS file. Using external Cascading Style Sheet rules and classes to format
a report is described in Formatting a Report With an External Cascading Style Sheet. CSS is used to control the style and layout of multiple web pages all at once.

At least
bigger than the p element and bigger
than the h2 element. But beyond trust
and hope, you don’t have any control over how your text appears. CSS is used to define styles for your web pages, including the design, layout, and variations in display for different devices and screen sizes. It was designed to enable the separation of presentation and content, including aspects such as layout, colors, and fonts. This separation improves content accessibility and provides more flexibility and control in the specification of presentation characteristics. CSS works by targeting HTML elements and applying style rules to define how they should be displayed, including properties like color, size, layout, and positioning.

CSS lets authors move much of that information to another file, the style sheet, resulting in considerably simpler HTML. And additionally, as more and more devices are able to access responsive web pages, different screen sizes and layouts begin to appear. Customizing a website for each device size is costly and increasingly difficult. The modular nature of CSS means that styles can be reused in different parts of a site or even across sites, promoting consistency and efficiency. In the last set of examples you saw that the text color of the
links turned blue without that being specified in the style sheet.

• The CSS font-size property defines the text size to be used.
• An external style sheet is used to define the style for many HTML pages.
• Just like the margin property, padding could have taken 4 values which would have been assigned to the top, right, bottom and left padding respectively.
• The modular nature of CSS means that styles can be reused in different parts of a site or even across sites, promoting consistency and efficiency.