Problem 1:

I downloaded the minecraft client from this website and i was able to launch it. My java is also up to date. I am also able to play in most of the servers. However, when the server or map selection screen comes up after you log in, it states at the bottom, ''choose a server above or paste a play.jsp URL below. Leave blank to generate a level.''

And so i wanted to generate a level, and i clicked go. And nothing happens. Does anybody know why this happened?

Problem2:

When i open up minecraft and i get to the login screen, i typed my username and password and i click single player and at times i get an error message or nothing just happens. Can somebody help me?

All help appreciated greatly.