Thanks for good idea! I use HAS CLASS=HIDDEN, when USER_ID is filled.
And described .hidden{display:none} in CSS file,
But would be nice to have READ ONLY also in Conditional States. Because some field might be only informative, visible and without possibility to change this by user. I see the page code for read-only fields is readonly="readonly", maybe there is an option to set for this field readonly="readonly" in Conditional States ???