This is rather a personal opinion. But when I'm alone, I tend to make a prototype first. This would be html, css and navigation, with fake data displayed.
I do this because it helps me focus when coding the logic behind it (give life to it). It's also useful to detect "holes" in your business logic before you do any complex coding, especially when dealing with clients. Because you can make all the specs you want, but clients will only see what's wrong once you show them the interface.