Everyday, we look at dozens of websites. The structure of these websites
is defined in HTML, the lingua franca for publishing information on the
web. Your browser's job is to render the HTML according to the specs
(most of the time, at least). You can look at the code behind any
website by selecting the "View source" tab somewhere in your browser's menu.
HTML consists of so-called tags, like the A tag for links, IMG tag for
images and so on. Since tags are nested in other tags, they are arranged
in a hierarchical manner, and that hierarchy can be represented as a
graph ... have fun!!!
http://gate.alltuto.com/?ai=060517