New CSS3 features such as animation, transition, and filters empower web designers to enrich the web pages with various types of interactivity and effects. Modern browsers, both on the desktop and mobile, are capable of rendering these CSS3 effects with the dedicated graphics processing unit (GPU) by using the compositing technique. There has been a lot of well-known CSS3 best practices, often centered around "use 3-d transform”. This talk sheds some more light on the browser interactions with the GPU and explain what happens behind the scenes, particularly for the objective of maximizing the synergy between the GPU and the CPU to have the most optimal CSS rendering performance.