matobodo on "Plugin character encoding problem"

I'm writing a plugin and i have problem with character encoding. i'm using characters e.g. (ľ,š,č,ť,ž,ý). Here is code:

add_action('admin_menu', 'receptar_admin_actions');
function receptar_admin_actions() {
    add_menu_page('Receptár', 'Receptár', 'manage_options', __FILE__, 'receptar_admin', plugins_url( __FILE__ . 'images/icon.png' ), 26);
}

i don't know how to fix it. i'm sorry if already is here this topic but i haven't found it

thanks for any help

Sorry for my english