This page contains content or formatting that is not valid. You can find more information in the affected sections - SharePoint 2010

Problem description:

You have an ASP.NET control that contains validation controls in the masterpage or page layout for a publishing site (an ASP.NET login control for example). When you try to edit and check in a publishing page you receive the following error.

Error message:

This page contains content or formatting that is not valid. You can find more information in the affected sections.

Resolution:

Million Thanks to Ari Bakker's SharePoint Config blog who helped me to resolve this issue. Please have a look, it’s too fabulous:

http://www.sharepointconfig.com/2007/09/asp-net-validation-controls-prevent-publishing-pages-from-saving

Product applies to:

-SharePoint Server 2010

-SharePoint Foundation 2010

References:

http://blogs.microsoft.co.il/blogs/justguy/archive/2008/08/13/checking-if-a-publishing-page-is-in-edit-mode.aspx

http://rhythmiccoding.blogspot.in/2010/09/this-page-contains-content-or.html

http://fahadzia.com/blog/2009/08/this-page-contains-content-or-formatting-that-is-not-valid-you-can-find-more-information-in-the-affected-sections/

http://junooni.wordpress.com/2011/02/08/error-this-page-contains-content-or-formatting-that-is-not-valid-you-can-find-more-information-in-the-affected-sections-important-statuspublication-start-date-immediately-important-statusstatus

http://sharepoint.stackexchange.com/questions/75664/error-this-page-contains-content-or-formatting-that-is-not-valid-you-can-find