
Finally... (after several days of study) I have discovered how to embed iframes into an html5 document and to avoid the validation errors, the scroll bar which inevitably presents itself, the issue with the deprecated "scrolling=no" and "marginwidth="0" and "marginheight=0" syntax.
Part One: Turning off the Scrolling Bar
First, I read a page on the web, (this page) which explained to prevent scrolling.. EDIT the file or (plural) FILE(S) which are embedded and load inside the frame, to turn off scrolling. It is futile to edit the main page itself. You do this:
That syntax...