A/B test

Running two versions at once to see which performs better, with the traffic split at random.

Decide the sample size and the stopping point before launch. Peeking at a running test and calling it when it looks good produces confident-sounding noise.

Test one meaningful change at a time. Redesigning the whole page tells you it worked, never which part did.

It converts opinion into evidence. On a page with real traffic, one settled test is worth more than a month of debate.