We are an open community of developers, technical writers, and learners building resources for a better Web, regardless of brand, browser, or platform. Anyone can contribute, and each person who does contribute has an impact on millions of readers. Learn how to contribute and drive innovation on the Open Web.| developer.mozilla.org
Specificity is the algorithm used by browsers to determine the CSS declaration that is the most relevant to an element, which in turn, determines the property value to apply to the element. The specificity algorithm calculates the weight of a CSS selector to determine which rule from competing CSS declarations gets applied to an element.| developer.mozilla.org
1. Delta specification| drafts.csswg.org
The Popover API provides developers with a standard, consistent, flexible mechanism for displaying popover content on top of other page content. Popover content can be controlled either declaratively using HTML attributes, or via JavaScript.| MDN Web Docs
