Texture problems

When I play i get a pink and black tiny little checkard box in the very top right of my screen its not big its hella small yet still annoying and i tried everything i unistalled then reinstalled wiped the materials then intsalled them back but it keeps happening

So what exactly does this do?

i mean like i unistalled evertything

Then installed it again?

Do you have the textures mounted? IE are you playing on a server that uses CSS without CSS? Also, try messing with your graphics settings, especially anti-aliasing iirc, then restart gmod.