From CyberWurx Customer Wiki

Basic Server Configuration

Changing RCON Password

Changing Server Hostname

Changing the MOTD

Left4Dead Specific Functions

Using host.txt for a Server Banner

Setting your Steam Group ID

Turning off the Lobby System

Current Known Bugs

Default L4D2 Config not allowing lobby

The default server.cfg had the following CVAR enabled:

sv_steamgroup_exclusive 1

This restricted lobby players from entering your server. If this cvar is set in your server.cfg and wish for the servers to be filled, please either comment this cvar out, or set it to 0.

//sv_steamgroup_exclusive 1

OR

sv_steamgroup_exclusive 0

For more information about sv_steamgroup_exclusive, see Setting your Steam Group ID and Turning off the Lobby System