Meet Brackets, Adobe's New Open Source HTML Editor
First of all, it has an innovative simplified user interface. Brackets doesn't come cluttered with many tools and panels. Instead, it puts puts context-specific code and tools inline so you have what you need just when you need it.
Second, a feature called Live Development allows Brackets to work directly with your browser so you can see the effects of your edits instantly. There's no copy and pasting of code, no switching back and forth between applications. You don't even have to refresh the view.
There's also a Brackets blog. And you can learn more about Brackets and other Adobe projects related to open source and web standards (like Adobe Shadow, Edge, and PhoneGap) at the Adobe & HTML website.
Here's an introductory video on Brackets: