Related Clues:

• They're prohibited
• Some rules
• They're off-limits
• Part of an etiquette list, maybe
• Things frowned upon
• Prohibited things
• Taboo actions
• Forbidden activities
• Inappropriate behavior
• Proscribed actions
• They aren't done
• Taboos (and title of this puzzle)
• They're proscribed
• Fashion faux pas list
• Don'ts