Updates to Left 4 Dead have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:

Left 4 Dead
Removed the "Are you ready to play Versus?" confirmation
Fixed a crash when using mouse wheel or keyboard to select Campaign chapters
Fixed sv_steamgroup_exclusive servers advertising for public lobbies
Restored the ability to vote for a new campaign in Versus mode
Get the full article at store.steampowered.com