Writing my first web application to design a storm sewer system, I'm studying a solution to load the proper form according to user selection. I will show you a provisional code to solve this demand. Now the style (texts, colours and graphics) of the web-app is ugly, I will write it last.
The CSS files in the default theme folder are an excellent starting point, because they are compatibles in almost all browsers and well tested, really in my site I modified and adapted the Bartik theme. Sometime modifications lead bad surprises in print style and so you need hide a few elements, secondly you can add two useful features: complete address in the links and signature under header.