$_SESSION errors

[LingoOutsider]

I'm trying to use $_SESSION for the first time.

When testing my script in EasyPHP everything works OK but when I upload I keep getting this message...

Cannot send session cookie - headers already sent

This is how I've used the code

page 1

 session_start();
// defalt testing login
$username = "myname";
$password = "mypassword"; 
$_SESSION['username']= $username;
$_SESSION['password']= $password; 

page 2

$username = $_SESSION['username'];
$password = $_SESSION['password'];

echo $password;
echo $username;