Understanding the CSS Cascade

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Published July 2014

Demystify CSS order, specificity and origin.

In CSS, the cascade is everything — there’s a hint why in its name. If you don’t understand how CSS rules are applied by browsers, you are in for a world of pain.

Over a series of five lessons, you’ll learn how browsers sort declarations to determine which selectors will “win”. The course includes a series of hands-on exercises on all aspects of the cascade from user style sheets to !important rules, specificity and more.

This course is taught by Russ Weakley, with a technical review by Aurelio De Rosa.

Oh yeah, and the whole SitePoint library! Learn More.

What you'll learn

The course covers:

  • The power and importance of CSS cascade: how it works, and why it’s important.
  • How to gather and sort your declarations based on origin and importance
  • Selector weight, and how to determine specificity
  • Understanding how the written order of CSS rules can have an impact
  • The future of the CSS cascade

  • Closed captions available
Meet your instructor
Russ Weakley

Russ is a world-renowned author, speaker and CSS expert. Russ has a detailed knowledge of Design and development. His expertise covers graphic design, interface design, site architecture and standards based development.

Lesson 1: Getting Started
Introduction to this Course 2:10
Types of Style Sheets, Normal vs/ Important Declarations & Conflict 5:08
Lesson 2: Sorting by origin and importance
Gathering and Sorting Declarations & Exercise 9:29
Lesson 3: Specificity
Determining the Selector Weight 9:07
Exercise on Specificity 9:35
Lesson 4: Order
Determining the Order Specified & Exercise 6:16
Lesson 5: The Future
The CSS3 Cascade 4:47
Lesson 6: Postscript
Override Declarations 2:01
Course Resources

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