-$lang['_valid_username'] = "You must enter an e-mail address or a valid username.";
-$lang['_do_login'] = "Wrong %s, or wrong %s.";
+// Login / Register/ Account / Profile
+$lang['_valid_username'] = 'You must enter a valid username with letters, numbers, . (dots) or _ (underscores).';
+$lang['_valid_username_or_email'] = "You must enter an e-mail address or a valid username.";
+$lang['_do_login'] = 'Wrong %s, or wrong %s.';
+$lang['_valid_date'] = 'Invalid %s! Use the specified format or leave the field blank if you don\'t want to specify it.';
+$lang['_valid_old_password'] = 'Wrong %s.';
+$lang['_change_password_cond'] = 'If you want to change your password complete all three password related fields.';
+$lang['_required_by_register'] = 'The %s field is required.';