ORDER IN WHICH ELEMENTS ARE LOADED
WHY IS THE LOAD ORDER IMPORTANT?
ASYNCHRONOUS LOADING: DEFER AND ASYNC TAGS
Important! Defer and Async tags are available only for external scripts (with src=”” tag). If you will try to use them for internal scripts like tags, defer and async will be ignored.
EXCLUDE UNUSED COMPONENTS OF .JS LIBRARIES.
Most developers use libraries like jQuery UI or jQuery Mobile as is. This means that the code includes all possible components of each library, when you may only need two or three.