I have solved this problem after many researches,
just comment two lines in meta_box.php file at end.
$sanitizer = isset( $field['sanitizer'] ) ? $field['sanitizer'] : 'sanitize_text_field';
to
//$sanitizer = isset( $field['sanitizer'] ) ? $field['sanitizer'] : 'sanitize_text_field';
at line 692 and
$new = meta_box_sanitize( $new, $sanitizer );
to
//$new = meta_box_sanitize( $new, $sanitizer );
at line 697
then you can save html or css in metabos editor.