contact your agent directly, Century 21 has multiple entry points for listings to be distributed, some come from the mls as a source which in most cases is trulia, while other come from other areas century21.com is created specifically by the Century 21 system for your home, so your agent can usally find our how trulia got it and correct it at the proper source, or go in to trulia and modify it him/herself.
With the sharing of so much information this is an occasional problem and your agent will be glad to hear about it and correct it in most cases.
Is your home listed with a Realtor? Many of the sites like this one take a directly from the MLS.
If you have any questions, please feel free to call me at (716) 743-5297.