iFrame parser error after upgrading to .NET 4.5

Question

We have recently upgraded all of our WebForms projects to .NET 4.5, and encountered a parser issue when loading pages with an iFrame element. We have corrected

Answer 1

You need to add the following tag:

and in the designer, change the control type to:

System.Web.UI.HtmlControls.HtmlIframe

Add the following in the Web.config:

This should fix it.