Source: View HTML Source Code of Webpage on Safari!

Source is an app plus a Safari extension that makes it easy to do one key web developer task: view the HTML source of any web page, with beautiful and customisable syntax highlighting. Just browse the web in Safari as you normally would, and if you want to view the source for your current page just tap the Action icon and choose Source. Make sure Source is enabled, then position it wherever you want it in the list of Safari actions, and tap Done.