Part of this can be handled through convention. We navigate websites because there is a convention that links are underlined and in color. This is a pretty crappy convention because it is ugly, unaesthetic. All those underlines and colors ruin the page layout. But one dare not change it because millions of people have come to rely upon this for navigation.
Web pages can describe what each item does.
So on the web, we know what to do by a combination of convention and description. Alas, most sites flaunt convention and are bad at description. As Jakob says, that is why the majority of uses of the web result in failure. You click, you wait endless seconds for the handshaking and then the download. And then you see you are in the wrong place.