Oct 09, 2018 05:15 PM|mgebhard|LINK
Google the error, there's a lot of information out there related to this error.
Otherwise, post the markup and code behind file(s) that caused the error. Lastly, the error is related to AJAX controls. If you are using 3rd party controls than see support for the 3rd party controls.
Also this is a bit odd
<!DOCTYPE html P'
it should look like.