A CSS filter is a coding technique used to hide or show CSS markup depending on the browser, version number, or capabilities. Browsers have different interpretations of CSS behavior and different levels of support for the W3C standards. CSS filters are sometimes used to achieve consistent layout appearance in multiple browsers that do not have compatible rendering.
Read more about CSS Filter: Prefix Filters, Commented Backslash, Box Model Hack, Underscore Hack, Star Hack, Star HTML Hack, Star Plus Hack, Child Selector Hack, Negation Pseudo-class Hack, Body:empty Hack, !important Quirks, Dynamic Properties, Conditional Comment, Criticism