One corollary to “use Web standards” (step 1) is “ensure separation of presentation and behavior from content” – one of the fringe benefits of doing so, as you’ve probably guessed, is improving page load and rendering times.
Just in case the browser cache is a nebulous thing that you’ve never quite understood, let me give a vastly simplified explanation. When a user enters a URL, the browser connects to a server and obtains some HTML. The browser parses the markup to identify external objects which need to be retrieved. The browser first checks the local cache to determine if any of those files have already been downloaded; if not, it proceeds to download those external objects. All of those objects will live in the browser cache for a period of time – exactly how long is determined by settings on the server as well as the user’s browser preferences.