This tab is for experienced web developers. It allows you to confine the styles that are applicable to the target elements. For example, a pinned to the top of the page header will have a style "sticky" added to the pinned group when the page is scrolled. So to add a background to the group when it is scrolled, you can add ".sticky " to the before selectors. Assume that the style with the background set is called "group-background". The preview pane will show this ".sticky .group-background".
Before selectors:
Selectors that are added before the current style.
