Blake Lively wore a beautiful dress by Marchesa, part of the Fall/Winter 2010 collection. The dress is one-shoulder and a striking blue, decorated with a pretty and elaborate floral detail. The shape, the design and the colour are what I love about this dress and what make it so unique.
Marchesa is known for it's stunning and graceful dresses (for an example, check out the post on Taylor Momsen's red carpet style). However, what I love even more about Blake's dress is that it's short. Blake manages to be elegant while still being age-appropriate, because after all, she's young and so should be having fun with fashion!