Using the SharePoint Solution Generator tool to create new list feature definitions
I discovered that the SharePoint Solution Generator adds a comment at the top of the generated aspx and schema.xml files for a list:
<!--
_filecategory="ListDefinition" _filetype="File"
_filename="DispForm.aspx"
_uniqueid="f3b8b185-2b24-4180-9854-e74d8d12ec75" -->
If this comment is left in the files when they are deployed, you will get an error when trying to view those pages:
"Only content controls are allowed directly in a
content page that contains content controls"
To correct the problem, just delete that comment line, rebuild the WSP file and redeploy.
Weird.