Re: Difficult to implement CSS1 bits

Chris Lilley already answered most of the points, let me just add one
more case:

Douglas Rand wrote:
> I've spent awhile reading the description of the various background
> attributes in the style sheet.  What particularly concerns me is the
> notion of "fixed" backgrounds.  This appears to be meaningless (or at
> least pretty useless) with the exception of the toplevel of the
> document,  i.e. a BODY or HTML background.  Was it really the intention
> to allow fixed, non-scrolling backgrounds on things like EM?

We needed it for the top level element, and disallowing it for other
elements would have meant introducing an unncecessary restriction. The
notion that "all elements are equal" creates a hurdle for implementers
that have to work with code from first generation browsers, but once
that hurdle is taken, many things become a lot easier, including
scripting and display of other formats than HTML (such as XML).

In addition, there is a case where it is useful: if the background of an
element has to be aligned with the background of another element. For
example, if you have a blue grid behind the document and a red one
behind the headings, you may want the red grid to be aligned with the
blue one. The only way to achieve that is to give them a common origin,
in this case the upper left corner of the window.