Master Page Weirdness - “Content controls have to be top-level controls in a content page or a nested master page that references a master page.”

Question

This is weird. I added a brand new Web Application project to my solution in Visual Studio 2008.

Created a master page. Made zero modifications. Created a new we

Answer 1

I encountered this error after editing a web part (.aspx) page in SharePoint Designer 2013. When I looked at the code in SPD, an H1 element near the top of the page was highlighted yellow. Hovering over that indicated that SharePoint:AjaxDelta was not closed before the H1. Adding the fixed it.

Weird because it appeared SPD introduced the error after I was working on listview web parts or a page viewer web part elsewhere on the page.