Ok, I have to say that just by simply adding this DOCTYPE declaration on top of a document was something. At first, I thought I was the only one having to deal with that issue. But, this is all around the net. When negotiating with a Web site in quirk mode, browsers will adjust as they see fit and will render the page accordingly to the best fit as possible. Over the years, I succeeded to obtain pretty much, up to the pixel level, the same layout across browsers. But, now that I am adjusting a Web site to work with this DOCTYPE declaration to be HTML5 compliant, it is a real nightmare.
I have done a lot of things so far to reorg everything such as normalizing the stylesheet, adding a few exceptions at the framework level to adjust accordingly to HTML5 or not and so on. But, this IFrame thing, this is something. What a complete waste of time it is. And, I still haven't figured it out completely. The alignment of a simple IFrame inside a DIV, so to have it centered turned out to be a real disaster. The javascript shows the proper IFrame.left and IFrame.top properties. However, the IFrame just does not want to move. The DIV it sits into is 100% in height and in width. I can bullet proof that the DIV is taking the entire area of the browser because it has a background and I can see it fits accordingly. But, I am trying to align the IFrame inside it, and when I work in HTML5, I just cannot move the IFrame container. This is things like that that irritates me. It's like when I had to learn a new development environment. But, this here, should be something that should have been resolved in a few minutes.