Yes, AP Stylebook Online provides a WYSIWYG (What You See Is What You Get) text editor for your custom entries and notes which provides the ability to style your content.
You can also use HTML to format your custom entries and notes. Examples include: <b>bold type</b> and <i>italic</i> text.
Individual subscribers and users who are part of a named-user site license can add custom entries and notes.
Concurrent-user license users cannot add custom content, just the account managers.
Please consult the User Guide for more information.