Hello,
We have pages which inherit Microsoft.SharePoint.WebPartPages.WebPartPage, in the publishing feature built-in Pages document library. We have our custom master page (more precisely, one that is specified as the Site Master Page for the site) with those pages, by having MasterPageFile="~masterurl/custom.master" attribute with the <%@ Page directive.
In SharePoint 2010, it works fine.
However, when migrated to 2013, it produces the error in the title i.e. not a valid.
Has anybody here had the same issue and overcome?
Thank you, Kazutsugu