These days it seems as if all the awesome people in the industry design in the browser. But you know what? It's hard to get in the flow when you are coding. Designs turn out blocky and bland.
It feels like the only way to master HTML and CSS is to spend years bashing your head into your keyboard while wrestling with floats and clearing divs in obscure browsers.
It's hard to be creative in the browser because there is a huge wall of technical nonsense between the design in your head and the browser.