CSR

CSS
like, for using to make websites look pretty!

CST

Central Standard Time

CSU

CSV

CSW

CSX

CSX Transportation - they're trains, i'm pretty sure.

CSY

CSZ

CTA

(I'm doing this correctly, right? Never been the first one to do an A before)

CTB

yep, you got it right! =)

CTC

(yes! Thank you.)

CTD

yep yep!

CTE

CTF

CTG