How Does Cascading Work in CSS?

Unveiling the "Cascading" in Cascading Style Sheets (CSS)

In the realm of web development, the term "cascading" holds significant importance in Cascading Style Sheets (CSS). It describes the mechanism by which multiple CSS declarations interact to determine the final appearance of an HTML element.

What Exactly Does "Cascading" Mean?

The term "cascading" refers to the process of selecting the appropriate CSS rule for a particular HTML element when multiple declarations are applicable. This process involves a systematic evaluation of declarations based on their specificity and order of appearance.

An Illustrative Example

Consider the following CSS declarations:

/* Stylesheet 1 */
body { font-size: 16px; }

/* Stylesheet 2 */
p { color: blue; }

/* Stylesheet 3 */
p.important { font-size: 24px; }

If the HTML contains the following element:

<p class="important">This is an important paragraph.</p>

The following cascading process occurs:

• The most general rule (body { font-size: 16px; }) applies to all HTML elements, including paragraphs (

  ).

• The second rule (p { color: blue; }) is more specific, applying only to paragraph (

  ).

• Finally, the third rule (p.important { font-size: 24px; }) is the most specific, applying to paragraphs (

  ) with the class ".important".

Since the third rule is the most specific, it overrides the other declarations. Therefore, the paragraph (

) will be rendered with a blue color and a font size of 24px.

Deep Dive into the W3C Specification

The official W3C specification provides a comprehensive explanation of the CSS cascading mechanism. By delving into its details, developers can develop a thorough understanding of how stylesheets interact to produce the desired appearance of web pages.

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