Artpunk00:
What doesserial.printInmean?
Note that it's print[b]l[/b]n, not print[b]I[/b]n. The two letters (capital i vs lower case l) look similar, especially in some fonts where they are identical but it's very important to get it right. The ln means that it starts a new line of text after that print, as opposed to Serial.print(), which doesn't.
Also, it's Serial, not serial. It's extremely important to be precise in computer programming. If you don't pay attention to small details like this you are going to have a really hard time.