Controls whether a reference to the required cascading style sheet (CSS) file for this control is automatically added to the page source.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
When this control is added to a page, it by default ensures that the menu-21.css file is referenced. The style rules in menu-21.css are required for the menu to function correctly. However, it may be desirable to include these style rules in a different CSS file that is already referenced in order to reduce the number of HTTP requests for CSS files. The Microsoft SharePoint Foundation default CSS file, corev4.css, also contains the necessary styles so if this file is already referenced from the page, this property may be safely set to false.