users.css - add error class style, old error and success classes renamed to errormsg and successmsg
getuser.php, reguser.php, login.php - adding strtolower function to lowercase user nick.
registration.php - delete <br> tag after error message.
taskedit.php - change input type from date to text
jquery.nickvalid.js, jquery.us_nickvalid.js - adding display error messages.
jquery.us_valid.js - change div classes to errormsg and successmsg
jquery.usersettings.js - add div with error messages (default invisible)
addtask.php - add lost variables for translated input POST elements $task_name $task_comm (fail, how is it?)