Ideas want to be ugly.
There's a superb article by Brad Frost on HTML wireframes. As he rightly states, "designing for a multitude of screen sizes, environments, and variables is hard work, so getting into the browser as quickly as possible gives us an opportunity to design and develop more realistic solutions".
This is a good reminder for a perfectionist designer/developer like myself. One of my recurring mistakes is trying to polish something up too early – rather than just getting the wheels turning and then little by little working on the finer details.