Why We Skip Photoshop is a 37signals piece that lists 7 reasons why they go straight from a paper sketch to HTML/CSS and skip the step of making a static Photoshop mockup when building web apps. Why We Don’t Skip Photoshop is a response to that article, listing 3 reasons why Blue Flavor doesn’t skip the Photoshop step. Both are worth reading, especially if you’re looking at your own web app design process.