Fires after creating the in the element for the custom css stylesheet.

Allow inserting CSS inline instead of through a separate file.

Filter the Custom CSS link enqueued in the head.

Do not include any CSS on the page if the CSS includes an error.Setting this filter to true stops any Custom CSS from being enqueued.

Fires right before printing the custom CSS inside the element.

Filter the Custom CSS returned from the editor.

Filter the default message displayed in the Custom CSS editor.

Filter the Custom CSS returned.Can be used to return an error, or no CSS at all.

Filter the array of available Custom CSS preprocessors.

Determine if a WordPress.com site uses a Free trial of the Custom Design Upgrade.Used only on WordPress.com.