The website uses one menu across every page instead of different menus everywhere.

Before, different pages had different menus. You'd land on a service page and the navigation didn't match the homepage. You'd have to hunt for what you needed. Every page has the same menu at the top.

It sounds small, but it makes the whole site feel like one thing instead of a bunch of separate pages bolted together. You can move around without relearning where everything is.

It's the kind of thing you don't notice when it works. You only notice it when you're lost. You won't be.