For some reason all of the folders within the Steam/steamapps/common/half-life/cstrike has been deleted. There is a backup available online at the link above and you can copy and paste the contents in your current cstrike folder. Be sure to backup files if needed and if it asks you to overwrite some files that you need (config.cfg, etc.) skip those files!
If you have backups of your cstrike folder, then you may not need to download from the link above at all.
You also may want to disable automatic updates for CS. You can do this by Right-Clicking the game in your Steam Library. Hit Properties, Updates tab, then disable Automatic Updates.
Hopefully Valve fixes their crap and get things back to normal real fast.
Good luck and happy gaming!
Top Poster: keN (4,294,967,295)