Retrieving Server Information Please Wait (Team Fortress 2)?

I just installed the F2P Team Fortress 2 yesterday. I'm having trouble accessing the server. Every time I click the Start Game, it always written Retrieving Server Information below. I've waited for around 10 minutes and still no respond. I'm able to access the offline practice and tutorial. When I click the join server, nothing shows up on the box. Just empty. How to fix this????