In the CSS panel of style edition popup:

• Page relative rules are in the first part of the text, ended by the special keyword .WS_PAGE_END {}.

The second part contains the rules for elements.

• In each part, named styles are before local styles.
• The selectors of a named style are prefixed with the element type they apply to.

.wstextarea_beautiful {...} or .wstextarea_beautiful a:hover {...} are rules of the style 'beautiful' applying to the wstextarea type (rich text in other words).
A named style can be modified and saved after selecting any element.

• The selectors for local styles are of the form <.id_xxxx>, where xxx is the ident (in HTML) of the targeted element.

.id_Y50744bbbe4284 {...} is a rule for the element which id is Y50744bbbe4284.
A local style is really modified and saved only if it applies to the selected element.

• @rules you have introduced are rejected at the end of text, uninterpreted by the interface.

To erase all @rules, you must type a pseudo rule at the end: @{}
This pseudo-rule will disappear at publication.