I am not associated with the site that you referenced in your original post.
I tried the site you mentioned in your original post on my my desktop and tablet, desktop worked fine until the browser was shrunk and then the page became similar to your original post:
Screen size greater than 800px
Screen size less than 800px
To try and clarify the confusion - recently I introduced a Shoutbox on a site that works for smartphones, tablets and desktops. Unfortunately a third-party advertiser abused the Shoutbox with their advert script using position:fixed . Their adverts completely screwed the CSS Responsive Design layout
The links I posted showed a screen dump of the offending third-party adverts.
I think this thread should be moved to the CSS Forum.