Postgres connection doesn't disconnect, only stay in idle status

Postgres connection doesn’t disconnect after using any application, only stay in idle status, the connection doesn’t dessapear on the DB server and if i use the same application o the same machine, and press F5 another connection is stablished and the first one is never disconnected. any idea ? my postgres 9.1 scriptaces 8.1 y my connection doesn’t have permanent connection checked.