Online Resource

Barker Library - TP754 J336 2019

Tverberg, Lois, author

Smith, David Raymond, author

Riches, Tanya, author

Stefan, Patrick G., author

What is the cascade?

The cascade is a mechanism for determining which styles should be applied to a given element, based on the rules that have cascaded down from various sources.

The cascade takes importance, origin, specificity, and source order of style rules into account. It assigns a weight to each rule. When multiple rules apply to a given element, the rule with the greatest weight takes precedence. The result is an unambiguous way to determine the value of a given element/property combination.

Browsers apply the following sorting logic:

• Find all declarations that apply to a given element/property combination, for the target media type.

• Sort declarations according to their importance (normal or important) and origin (author, user, or user agent). From highest to lowest precedence:

  1. user !important declarations
     
  2. author !important declarations
     
  3. author normal declarations
     
  4. user normal declarations
     
  5. user agent declarations

• If declarations have the same importance and source, sort them by selector specificity.

• Finally, if declarations have the same importance, source, and specificity, sort them by the order they are specified in the CSS. The last declaration wins.

What is specificity?

Specificity is a method of conflict resolution within the cascade.

Specificity is calculated in a very particular way, based on the values of 4 distinct categories. For explanatory purposes, the CSS2 spec represents these categories using the letters a, b, c, and d. Each has a value of 0 by default.

• a is equal to 1 if the declaration comes from a style attribute in the HTML (“inline styles”) rather than a CSS rule with a selector.
• b is equal to the number of ID attributes in a selector.
• c is equal to the number of other attributes and pseudo-classes in a selector.
• d is equal to the number of elements and pseudo-elements in a selector.

The specificity is given by concatenating all 4 resulting numbers. More specific selectors take precedence over less specific ones.

For example, the selector #id .class[href] element:hover contains:

• 1 ID (b is 1)
• 1 class, 1 attribute selector, and 1 pseudo-class (c is 3)
• 1 element (d is 1)

Therefore, it has a specificity of 0,1,3,1. Note that a selector containing a single ID (0,1,0,0) will have a higher specificity than one containing any number of other attributes or elements (e.g., 0,0,10,20). This is one of the reasons why many modern CSS architectural patterns avoid using IDs for styling purposes.

What is inheritance?

Inheritance is distinct from the cascade and involves the DOM tree.

Inheritance is the process by which elements inherit the the values of properties from their ancestors in the DOM tree. Some properties, e.g. color, are automatically inherited by the children of the element to which they are applied. Each property defines whether it will be automatically inherited.

The inherit value can be set for any property and will force a given element to inherit its parent element’s property value, even if the property is not normally inherited.

About !important

The above should make it apparent that !important is a separate concept to specificity. It has no effect on the specificity of a rule’s selector.

An !important declaration has a greater precedence than a normal declaration (see the previously mentioned cascade sorting logic), even declarations contained in an element’s style attribute.

[CSS terminology reference]

Translations

• CSS: каскад, специфика и наследование

Of the 1,089 new cases, Mumbai accounted for 748, with a cumulative tally of 12,142. With 75 new cases, Pune district’s tally has risen to 2,537.

Council of Supply Chain Management Professionals, author

Leland, Karen

Freedman, Rick, author

Runion, Meryl

Munson, Chuck, author

Stanek, William R., author

Zacker, Craig

Bishop, Russell, 1950-

Interview with Rebecca N. Dudovitz, MD, MSHS, author of Assessment of Exposure to High-Performing Schools and Risk of Adolescent Substance Use: A Natural Experiment

Interview with Robert W. Yeh, MD, MSc, MBA, author of Temporal Trends in Unstable Angina Diagnosis Codes for Outpatient Percutaneous Coronary Interventions, and David L. Brown, MD, FACC, author of Gaming, Upcoding, Fraud, and the Stubborn Persistence of Unstable Angina

Interview with Amanda H. Kerbrat, MSW, author of Effect of Augmenting Standard Care for Military Personnel With Brief Caring Text Messages for Suicide Prevention: A Randomized Clinical Trial

Interview with Roberta W. Scherer, PhD, and Craig Formby, PhD, authors of Effect of Tinnitus Retraining Therapy vs Standard of Care on Tinnitus-Related Quality of Life: A Randomized Clinical Trial

Interview with Stephen W. Waldo, MD, author of Association of Coronary Anatomical Complexity With Clinical Outcomes After Percutaneous or Surgical Revascularization in the Veterans Affairs Clinical Assessment Reporting and Tracking Program

Interview with Naiyer A. Rizvi, MD, author of Durvalumab With or Without Tremelimumab vs Standard Chemotherapy in First-line Treatment of Metastatic Non–Small Cell Lung Cancer: The MYSTIC Phase 3 Randomized Clinical Trial

McKeever, William, author

Henderson, M. H. (Margaret Helen), author

Rotch Library - KF665.Z9 J638 2018

Dewey Library - K3585.E653 2019

Dewey Library - K5261.F76 2019

Dewey Library - KF3775.E548 2018

Dewey Library - KZ6471.S27 2019

Dewey Library - K3260.W38 2020

Dewey Library - KF3958.A3282016 A2 R68 2018