HTML pages inside other pages

I am building content in HubSpot, which is a complete website development environment, and is the web server I have available.

I have successfully inserted interactive SWF-based Captivate content inside pages created in HubSpot and they work fine.  The Captivate content appears as a window on the web page and works correctly.

Now I would like to do this with HTML 5 content, but when I do  I only get a blank screen, where the HTML 5 content should play.

I took out the first and last lines (html headers) but that did not help.

Has anyone had any experience with something like this, or have any ideas on why the HTML 5 doesn't work, or suggestions for what I can try.

I carefully built the HTML structure in the online file manager, so I don't believe that is the problem.

Thanks.