Libraries for enabling the use of modern CSS features in legacy browsers.

• Selectors
• Properties
• Values
• Other

A selector determines the set of elements within a web page that should be styled. e.g. p, .banner

• :focus-within
  • focus-within

A property specifies what aspect of a selected element's styling should be changed. e.g. color, font-size

• object-fit and object-position
  • object-fit-images
  • object-fit-videos

A value defines the property's setting. e.g. red, 20px

• sticky (position)
  • stickyfilljs

Miscellaneous other features and capabilities of CSS.

• The Web Design Academy - CSS Glossary