add "How come my form is blank?" to FAQ

doc/manual/FAQ.markdown

@@ -348,4 +348,21 @@ Hobo controllers contain methods that ensure that those two variables always hol
 
      @foos = Foo.all
      self.this = Foo.all
-     @foos = self.this = Foo.all
+     @foos = self.this = Foo.all
+
+# How come my form is blank?
+
+The most likely cause of forms not displaying is due to permission errors.   Read [The Permission System](http://cookbook.hobocentral.net/manual/permissions) and check your `attr_accessible` declarations.
+
+If the entire form is missing you can add alternate content through an else clause:
+
+    <form/>
+    <else> No permission to display form </else>
+
+It's also possible that the form is displaying but none of the fields are.   You can force the display of the fields with
+
+    <form>
+      <field-list: force-all/>
+    </form>
+
+You probably don't want that in production code, though!