An arrangement for enabling declarative show and hide animations in web-based applications is provided in which expando attributes associated with HTML elements are utilized to define CSS level 3 (“C553”) animations that are executed when an element is shown or hidden. A set of utility functions, which wrap standard DOM (Document Object Model) element methods supported in JavaScript, are employed to show, hide, add, and remove elements from the DOM tree and invoke an algorithm when used. The algorithm traverses the DOM tree for HTML elements that have the show and hide expando attributes and automatically executes the associated animations.