diff --git a/gen/__init__.py b/gen/__init__.py
index 71d9ca9..fab117b 100644
--- a/gen/__init__.py
+++ b/gen/__init__.py
@@ -1993,33 +1993,36 @@ class Ref(Type):
     def mayAdd(self, obj):
         '''May the user create a new referred object from p_obj via this Ref?'''
         # We can't (yet) do that on back references.
-        if self.isBack: return
+        if self.isBack: return No('is_back')
         # Check if this Ref is addable
         if callable(self.add):
             add = self.callMethod(obj, self.add)
         else:
             add = self.add
-        if not add: return
+        if not add: return No('no_add')
         # Have we reached the maximum number of referred elements?
         if self.multiplicity[1] != None:
             refCount = len(getattr(obj, self.name, ()))
-            if refCount >= self.multiplicity[1]: return
+            if refCount >= self.multiplicity[1]: return No('max_reached')
         # May the user edit this Ref field?
-        if not obj.allows(self.writePermission): return
+        if not obj.allows(self.writePermission): return No('no_write_perm')
         # Have the user the correct add permission?
         tool = obj.getTool()
         addPermission = '%s: Add %s' % (tool.getAppName(),
                                         tool.getPortalType(self.klass))
         folder = obj.getCreateFolder()
-        if not obj.getUser().has_permission(addPermission, folder): return
+        if not obj.getUser().has_permission(addPermission, folder):
+            return No('no_add_perm')
         return True
 
     def checkAdd(self, obj):
         '''Compute m_mayAdd above, and raise an Unauthorized exception if
            m_mayAdd returns False.'''
-        if not self.mayAdd(obj):
+        may = self.mayAdd(obj)
+        if not may:
             from AccessControl import Unauthorized
-            raise Unauthorized("User can't write Ref field '%s'." % self.name)
+            raise Unauthorized("User can't write Ref field '%s' (%s)." % \
+                               (self.name, may.msg))
 
 class Computed(Type):
     def __init__(self, validator=None, multiplicity=(0,1), index=None,
diff --git a/gen/ui/appy.css b/gen/ui/appy.css
index be46b44..485516d 100644
--- a/gen/ui/appy.css
+++ b/gen/ui/appy.css
@@ -102,8 +102,8 @@ img { border: 0; vertical-align: middle}
 .section2 { font-size: 110%; font-style: italic; margin: 0.45em 0em 0.2em 0;
             border-bottom: 2px solid grey; }
 .section3 { font-size: 100%; font-style: italic; font-weight: bold;
-            margin: 0.45em 0em 0.1em 0; background-color: #F4F5F6;
-            text-align: center; color: grey; }
+            margin: 0.45em 0em 0.1em 0; background-color: #95a1b3;
+            text-align: center; color: white; }
 .odd { background-color: white; }
 .even { background-color: #F4F5F6; }
 .summary {margin-bottom: 5px;}