What should be above the fold on a store?

What you sell and why here rather than elsewhere, in one line each. On a product page: the item, the price, and when it arrives.

In more detail

What should not be there: a slideshow, a newsletter pop-up, and a cookie banner covering the price. All three occupy the space in which a visitor decides whether to stay.

What to do about it

The photograph is usually the product page. Everything else is supporting it.

Most design decisions on a store are really navigation decisions, and navigation is what decides whether somebody finds the thing they came for.

A product page has one job. Everything on it that is not helping somebody decide is in the way.

The mobile app angle

The same screen designed several ways is the point: a catalogue of four hundred lines needs a different home screen from one of forty.