I've just found out that cyrillic goes fine only when encoding in the browser set up on cyrillic during I type the message

Every time I go to 'Sign Guestbook' form encoding jumps back to ISO
Then each time I have to set encoding to cyrrilicWindows and type my message - no error message, all goes ok

But when it switches back to general guestbook view the encoding jumped back to ISO

Please advice how to leave encoding alone, how to edit *.php files so they wont set ISO encoding