Web browsers are one of the core applications on smartphones and other mobile devices, such as tablets. However, web browsing, particularly web page loading, is of high energy consumption as mobile browsers are largely optimized for performance and thus impose a significant burden on power-hungry mobile devices. With the advent of modern web capabilities, websites even become more complex and energy demanding. In the meantime, slow progress in battery technology constrains battery budget for mobile devices. As users are more aware of energy consumption of apps, it is desirable to improve the energy efficiency of web browsing, particularly web page loading.