Flea collars are ugly, smelly and don't always work very well.
They really have been superseded by better products, such as Advantage. Pop into a vet and purchase "Advantage for puppies" or another flea product. Be sure to tell them the age of the pup so they sell you the right product. They work out cheaper than flea collars in the long run, and work fast, killing most fleas within the first 24 hours. Supermarket flea products arent very good and contain chemicals that can be harmful to pets.