HTML5 problems

Hi,

I keep experiencing difficulties with my courses when I post them online using html5. Here is an example:

http://www.sefad.ca/dfqc/test/presentation_html5.html

If you go to section 4.7, it is a slide created with Engage '13. Sometimes it loads, sometimes it just tries to load, but never does (see attached screen shot).

Also in section 4.8.2, 4.8.4 and 4.8.6, it is a quiz created in Quizmaker '13, but not all answers in the drop down menu are accessible.

When I try in the non-html5 version (http://www.sefad.ca/dfqc/test/presentation.html), none of these problems arise. I've also noticed that there's more problems when using Firefox than when using Chrome. Is there a reason for that?

Thank you,

Melanie