The difference is they don't use javascript, a point many commenters apparently missed. This is similar how you can make drop-down header menus in css only - no

The difference is they don't use javascript, a point many commenters apparently missed. This is similar how you can make drop-down header menus in css only - no javascript. Implementing css dropdown menus was one of my first big web dev tasks, since many users still had computers that slowed to a crawl when javascript and dom manipulation were involved.