How a page arrives

From typing an address to pixels.

The sequence

The browser resolves the name, opens a connection, requests the document, then requests every stylesheet, script, image and font it references, building the page as they arrive.

Stylesheets block rendering; scripts block parsing unless deferred.
Every extra request costs a round trip, which matters most on mobile networks.

Client and server

The server decides what to send and the browser decides how to show it. Anything sent to the browser is visible to the user, which is why validation must be repeated on the server.