i just sended a suggestion to stuff, the main problem on preview iframe is the not self-closed body description tag at the begining of the code. Is just that, a simple minor change, and i´m sure the rest of the errors will gone. If you take a deep look to errors and html code, you will see what i´m talking about.
Many times, if you have a big error on, let´s say, the body tags, the rest of the html can´t be processed the right way by w3c validation system… so, from there many others errors appears, but are not real.
In my opinion the preview has only 1 error and that´s the not sefl-closed tag. That´s all.
The home page, is some other thing i don´t have time right now to see deeply.