Here’s a neat little trick: Hitting the Esc key will kill web page loading in both Safari and Chrome. This can be useful if you’re visiting either a site packed so full of data that it’s crushing your computer, or a site that’s not responding.
Esc also used to stop animated .GIFs playing, but that doesn’t seem to work any longer.
Interestingly, the old Mac keystroke of Command+. will also do this. (And I’ll bet you didn’t know that Command+. sends Ctrl+C when you’re working in the Terminal window.)