The only way to truly tell a difference between real and fake designer bags is by taking them to the designer store. If you take your gucci bag to a gucci store they will be able to authenticate it for you. No website would be able to do that as its the detials in the stitching, zippers etc that gives them away.

Also I think if you are spending 500 bucks on a purse, its best to buy it from a real store and not online (unless its from the designer site itself like gucci.com)

Good luck!

ps- plz give me a best answer :) thanks