There's something a wee bit awkward in there now. How about:

Content can be resized to 400% without loss of content or functionality, and without requiring two-dimensional scrolling, except...

Actually, I'd also remove that comma after scrolling since the exception is about 2-d scrolling, right? As well, I think the final "to" should be 'for'

Content can be resized to 400% without loss of content or functionality, and without requiring two-dimensional scrolling except for parts of the content where fixed spatial layout is necessary for use or meaning.

merged to FPWD_review