If you write AB tests with jQuery you have to make sure you write your code as optimised as possible. Every millisecond you shave off results in less chance of unwanted repaint or reflow flickers. Update: Tip number 1: Do NOT use jQuery! Why wait for a library to load, when vanilla JS nowadays does everything jQuery does - but faster. Use Faster Selectors. Know which selectors perform the fastest to optimise your code! // ID selector - very fast … [Read more...] about AB Test jQuery Performance Cheat Sheet