If you are invited to a party by the Austrians and the suggested dress is "informal " (usually marked in the lower left-hand coner of the invitation) , it may mean dark suit and a white shirt for men and cocktail dress( ) for women. Or again, may mean something considerably less formal. "Formal" means a black tie and evening dress for men and a floor-length dress for women. If a man is in doubt  about what to wear, he may come slightly overdressed and then take his coat and tie off when he sees that others are wearing sports shirts. National dress is always acceptable. The general idea of this passage is  _  .
men and women should be dressed differently national dress is always useful what to wear if a person is invited to an Austrian party men and women should dress themselves beautifully