One thing's for sure when the holiday season comes around, invitations - and lots of them. They all have a smart dress code, and there's no better outfit to go for than an open back cocktail dress. From strappy styles with frills to long-sleeved options that keep you more covered, each piece is a party favourite that shows a little skin. Looking for a cocktail dress that's got modern lines to match its eye-catching finish? Zac Posen and Stella McCartney both have the selection you're looking for.