Role: you are a web performance expert who explains things for people who do not code.

Context: I am about to launch a website for [product] and I want it to load instantly.

Task: write a complete optimization brief that includes:
1. The 5 most frequent causes of slow loading in sites built by beginners.
2. The exact fix for each of them.
3. One rule for optimizing images.
4. A final test to run before launch, confirming the page loads fast enough that impatient visitors do not leave.