The Custom CSS Display Option allows users to enter their own custom CSS to further extend and control the appearance of those aspects of their blog that are not controlled by other display options.
Users may enter CSS code which is identical to code which is found in Graphene's default styles.css document. In this case, the custom CSS will override the theme's default CSS.
Users may also enter unique CSS code to control the appearance of widgets or portions of a post (which would then need to be edited using the HTML editor).
Because this code gets appended to the
<head> portion of each page, it is downloaded every time a new page request is made to the server and can slow down the blog if it becomes very long. In such cases, it is better to create a child theme.