I love visualizing information. It helps people, all people, better understand systems, financial data, and life. This website does something amazing. It visualizes all the links, tables, tags, images, forms on a website and visualizes it as a graph. It's tough explain but here's a cheat sheet with some examples:

blue: for links
red: for tables
green: for the DIV tag
violet: for images
yellow: for forms
orange: for linebreaks and blockquotes
black: the HTML tag, the root node
gray: all other tags