This document compares CSS3 and jQuery for selecting elements, manipulating HTML elements, and animating elements.
CSS3 allows for robust element selection using pseudo-classes like :first-child and :nth-child(n). Both CSS3 and jQuery can toggle element visibility for drop-down menus. CSS3 introduces transitions, transforms and keyframe animations for animating elements, while jQuery has animation methods like .animate(), .fadeIn(), and .slideToggle(). CSS3 and jQuery can both be used to validate HTML forms, with CSS3 using pseudo-classes and jQuery using plugins. The document recommends using jQuery and CSS3 together to take advantage of their complementary capabilities.