Autoprefixer automatically adds vendor prefixes to your CSS rules, as needed, based on a configuration. And the configuration lets you do cool stuff like "Make my CSS compatible with all browsers that have >2% market share." You may already be using autoprefixer, but do you know which rules your configuration will actually generate? This online version lets you quickly test your CSS against different configurations to ensure you're getting exactly what you want.
We have long lamented the current ecosystem of hackable WYSIWYG editors in the world. For a long time, just about all of them have been driven off of contentEditable and raw HTML. But raw HTML is just so limiting. Couldn't we do so much more, far more cleanly and easily, if the state were defined in terms of pure data? Couldn't our user-created content be richer if we were less bound by the limitations of dumb HTML? Draft.js, one of the latest Facebook announcements to come out of Reactconf, is here to save us all. From its docs: "A string of plaintext is insufficient to represent the complex state of a rich editor." Amen.