I seem to be asked this a lot so i thought i would mention this online so hopefully people will no longer ask me, they’ll find the answer when they ask google
You are trying to inherit from a masterpage and you recieve the following error
the page has one or more < asp:content> that do not correspond with < asp:ContentPlaceHolder> controls in masterpage
Script tags are the culprit around 80% of the time. For some reason the visual studio designer doesnt like not fully closing your script tags at design time.
Change all of you script tags from this
Any you should be good to go.