I have a problem with connecting...
I have a 1.7 patch, but when I apply it, I keep getting disconnected when i try to connect to most servers (if not, there is another problem, for example that the map I have differs from the server's), getting a message that the server is using a different class table. On the internet I found out that it means the version of the server lags. A day later, this was still the problem (but people indicated that it is usually solved soon). So I re-installed it, but now most servers are unavailable because they are using a different protocol (15).

What to do?

Either:
A) You didn't fully download the Valve updates through Steam for you're Team Fortress 2
or
B) The servers you are trying to join have not yet downloaded the newest updates and thus do not match the client-side versions of the game.