Is there a essential set of downloads I should download?

[guitarman1400]

In some games the walls and some things are checkered purple and black. Also I see giant red "ERROR"s

How can I fix this?

[_nonSENSE]

The server is most likely using CS:S or TF2 models / textures.

[guitarman1400]

ah yeah it was probably CS:S. But is there a list of things i should download?

[nutnuts]

No. Just get CSS, most maps these days use a lot of CSS textures and models and server admins use a lot of their playermodels.