Very often, when you are negociating a new Web site for your organization or company, the Web designer will hand over a photoshop mockup of your Web site. Personally, I have a tendency to ban this practice. I prefer to receive a solid xhtml/css mockup and sees how it is handled in different devices.
The community around SVG is building up a new Web site. They decided to use SVG for the wireframe mockup of their Web site.