Consider the following scenario:
Or
- A custom list has a custom lookup field that references another custom list that contains more than 20 items in Microsoft SharePoint Foundation 2010.
- You add an item to the second list.
- You set the value of the lookup field to "None."
- You try to save the list.
The list item could not be inserted or updated because invalid lookup values were found for the following field(s) in the list: [name].
Or
- A custom list contains more than one field that references another list that contain more than 20 items in Microsoft SharePoint Foundation 2010.