These two tools are built into your browser
These tools are invaluable in coding, but for design they answer the question "How'd they do that?"
View Source provides the raw files, before anything happens
Right-click to show the contextual menu, then click "View Source"
Command-U or Ctrl-U
Core elements of HTML, and how they're used "in the wild"
How is a page built? Use the find command: Command-F or Ctrl-F to find common elements
This can help you see how others design their files and their code
View Source, but for the DOM, not the files
Updates in real-time