Without sounding like a real a___hole, I would suggest starting from scratch.
The rendered source code alone renders with 34 errors (W3C Markup Validation Service) and 52 warnings (HTML tidy)
Nesting of elements is a major problem - "p" tags in "p" tags are not allowed, having "span" tags span a huge block of code is also not allowed when other mark-up elements are within.
Standard HTML is being mixed with XHTML and Font Tags are also being used (The <font> tag in HTML is deprecated)
After you have the basic structure working properly you can then add your third party elements - iFrames etc.
At the same time I would check the Ditto templates/chunks for correct (X)HTML mark-up.
If you have a good base, then it should be easy enough to find where the problem is - trial and error, remove one bit at a time and you will find the culprit.
Happy hunting