White and blue checker board type thing always shows up

There’s a problem where I have this error-checker board thing like HL2 except blue and white, not black and neon purple. I never really knew what it meant.

I also don’t know how to make a legit topic because of not knowing this error.

That appears to be the default image when there isn’t one defined (you see this texture at the back of the crusher in Caustic Caverns). I take it you’re on Steam? Have you verified the integrity of the game cache? (in Steam, right-click the game title, select Properties, go to the Local Files tab, and click the ‘Verify Integrity of Game Cache’ button). I’d start there.

Ohhhh, thank you! I forgot about that little thing.
It’s always there but so discreet.