Built in FTP client (cmd + k) - can't upload files (Mavericks)
The built-in ftp is read only since forever unfortunately. From Mavericks help:


  Servers and shared computers that you can connect to
  
  You can connect your Mac to the types of servers and other computers
  listed here.
  
  ...
  
  
  FTP servers
  
  
  With read-only access, you can copy files from the server, but to copy
  files to the server you may need another FTP app. Choose Apple menu >
  App Store to find FTP apps available for OS X.


Maybe try the free Cyberduck or (not free) Transmit.