Adding this.DelayedViewItemsInitialization = true; removes all fields on the detailscreens. I've currently disabled this line, enable it to see the effect on the first menu item (cursussen and it's detailview)
See Also:
XAF – Detail View Performance Improvements (Coming in V2010 Vol 2)
We have closed this ticket because another page addresses its subject:
Layout.Web - Provide the capability to load tabbed groups content dynamically