To me, building web prototypes must be a lot like designing cars.
Step1: First you sketch out the basic layouts and place the essential functional elements in their ideal locations. We photograph these basic layouts which we sketch on a large whiteboard. The photos are shared with the design team and the client to ensure we have the basics right.
Step 2: If you like what you see you start to render the design in ways that brings additional value to the layout and enhances the features. We’re all familiar with car concept drawings like those of Chip Foose on the TLC television show "Overhaulin".
Step 3: Once the drawings or Photoshop designs are looking like the images you had in your mind all along the next step is to build a prototype. Car designers use clay to do this. Web designers code their designs into HTML/CSS. Customers, partners, investors and user experts can then get a sense of how this product will live in real space. By coding the design you allow target users to take the website or web application for a test drive.