YellowPencil does not write the CSS codes to the theme files, so customizations will not be lost. Customizations are safe in the database.

However, if a significant change has been made to the theme, some CSS selectors may no longer be valid. Remember, CSS selectors, are the address of HTML elements. Styles cannot be applied if the HTML element’s classes, the id names change. If such a problem occurs, you can update CSS selectors manually by using CSS editor.