So I am going to a movie premiere in Boston with a friend this weekend and there is a cocktail party before the screening...apparently the invitation specified "cocktail attire". What, exactly, does that mean? Not sure that anything I have is appropriate, other than a couple of sleeveless knee-length dresses that really seem more suitable for summer unless I wear tights and some sort of cardigan or wrap with them...dressing in clothes that are completely inappropriate for the conditions (like a sleeveless dress this time of year...I know the party is indoors but who knows if one might get stuck somewhere along the way and not be inside where it's warm?) just feels wrong to me. Would a longer (dressy) skirt with a cute top be appropriate, or would that be a big faux pas? As for shoes, I don't do heels so it will definitely be ballet flats. Any suggestions would be helpful...I am completely out of my element with events like this.