Steam and Internet Explorer 7
Not long ago one of my machines stopped being able to join our Counter-Strike server at CS.WallWorm.com . I figured that it must be due to my firewall. But even after disabling Norton Internet Security, the computer could not connect. In fact, it could not connect to any servers on my favorites list—though it could connect to other servers.
I re-installed Steam. Still, I could not connect. Steam would get as far as saying "precaching resources” but then simply drop and throw me back to the desktop.
After a little research, I found the problem. This machine was the only machine running Microsoft Internet Explorer 7 Beta. I had installed it to preview the kinds of changes I need to prepare for since my occupation is web development. According to SteamPowered.com… IE7 is not compatible with Steam.
I removed IE7 and suddenly everything is back to normal. So, if your Steam game is suddenly unable to connect to your favorite server and you are running IE7, try uninstalling IE7 and go back to Internet Explorer 6 until the final version of IE7 is released.
2011-11-10 This article is extremely dated but may potentially be useful for anyone who is unable to keep their browser up-to-date. (IE9 is currently the browser of choice with rumors of IE10 already circulating.)