You can easily edit both internal and external rules that you have applied to a document.
When you edit a CSS style sheet that controls the text in your document, you instantly reformat all of the text controlled by that CSS style sheet. Edits to an external style sheet affect all the documents linked to it.
You can set an external editor for editing style sheets. For information about setting up an external editor, see Starting an external editor for media files.
The changes you make are immediately applied to the current document, allowing you to preview your changes as they are made. If you are editing rules stored in an external style sheet, be sure to save your changes to see your updates applied.
If you modify CSS rules that are in a style sheet used by more than one document, those changes will be reflected in those pages as well.