I have a very strange problem with Counter Strike Source. I download maps from internet, install them, place every file in its folder in case there are more files than the main map file, I load it and, in most cases, most of the textures are missing. Shouldn't these textures be included with the map in the case that it uses different textures from the ones included in the standard game. I can see red errors and chequered textures eveywhere. How can I fix this problem? I've already downloaded several maps from fpsbanana and only one of them is completelly fine.

unfortunately it happens to me too, and very often, i have cs source fusion pack, i dunno if it affects the downloaded maps, maybe the maps are made only for source or maybe the textures are missing. but try downloading maps from very good sites. Maybe i f you do, the maps downloaded will have all the textures and files needed for playing wothout this red ERROR or PINK texture.
alright se'ya

are the files going into the right folder? just a thought