impure client detected. invalid iwd files referenced

when i played with mods i gett this error .... impure client detected. invalid iwd files referenced

help plz

You used ModLoader?

first i runed the game and then i type fs_game mods/RealisticSnD;vid_restart
efter that i i havee been the host but when the map loader i gett this error impure client detected. invalid iwd files referenced