Well according to my dictionary "Websterers II" (and I agree):
DESIGN: 1. A drawing or sketch. 2. The order or arrangement of the components and details of something in accordance with a plan. 3. A plan : project *syns: Blueprint, idea, layout, plan, scheme
DEVELOPMENT: 1. To realize the possibilities of. 2. To grow, unfold or expand gradually. 3. To make more available or effective. 4. To elaborate or enlarge 5. To progress from earlier to later stages of maturation.
Hope this give you an understanding.
Simply put a design is a picture and development is making the picture better!
