If you continue to have problems finding any servers, please exit from Steam, and then delete the following files from your Steam\config directory.
C:\Program Files\Steam\config\serverbrowser.vdf
C:\Program Files\Steam\config\masterservers.vdf
Your network must be configured to allow Steam access to the following ports:
Steam Client
* UDP 1200 (For the Friends service)
* UDP 27000 to 27015 inclusive
* TCP 27020 to 27050 inclusive
Dedicated Server
* UDP 27015 and 27020 (Default HLDS, SRCDS and HLTV ports)
* TCP 27015 (SRCDS Rcon port)
Note: Windows XP SP1 firewall users running Source Dedicated Server must open TCP Port 27015 for Rcon to work
C:\Program Files\Steam\config\serverbrowser.vdf
C:\Program Files\Steam\config\masterservers.vdf
Your network must be configured to allow Steam access to the following ports:
Steam Client
* UDP 1200 (For the Friends service)
* UDP 27000 to 27015 inclusive
* TCP 27020 to 27050 inclusive
Dedicated Server
* UDP 27015 and 27020 (Default HLDS, SRCDS and HLTV ports)
* TCP 27015 (SRCDS Rcon port)
Note: Windows XP SP1 firewall users running Source Dedicated Server must open TCP Port 27015 for Rcon to work