Custom map working ok for me, it shows errors for my friend

I made a dedicated server for my friends. I and my friend downloaded this map: http://www.garrysmod.org/downloads/?a=view&id=83458
We both installed it and for me, it works fine but he is seeing all these error models and pink/black square textures. I put it in a server also.

I was thinking that maybe it’s because he doesn’t have CSS and HL2 + episodes?

Thanks

Yes. Maps can use content from games. Maybe you own the game and he doesn’t.