Portals; widget.UI.MsgBoxInfo and related functions may not appear to work correctly

If a Portal page accesses the widget.UI object (e.g., to display a message box) but does not include the HTML Widget CSS resource, display issues may occur. To alert Portal developers to this, the summary below the grid on the Portals form, Pages page now displays the following warning if this condition is detected:

This page references the widget.UI object but the 'CSS Stylesheet for HTML Widget' resource is not included. This may result in display issues such as message boxes being invisible.