Cross browser simple solution with no images and no extra markup? Not gonna happen, does not exist, don’t even waste your time TRYING.
Best solution is the extra div and an image - BUT, you don’t need 8 div or 8 separate images to do it, you can do it with ONE image and 6 div, the deepest ‘nesting’ being two deep.
<div class="borderTop"><div></div></div>
<div class="borderFirstSide"><div class="borderSecondSide">
Content goes here
<!-- .borderFirstSide, .borderSecondSide --></div></div>
<div class="borderBottom"><div></div></div>
The top div pairing is a sliding-doors effect for the top, sliding doors with repeat-y for the ‘sides’, and a third sliding doors pairing at the bottom.
I call the technique “Eight Corners Under One Roof”, and made a page a while back explaining one approach to doing it. The same technique can be used for rounded corners, or any other all-around the content effect you can think of.
http://battletech.hopto.org/html_tutorials/eightcorners/template.html
I have a page showing it applied to existing div by class using javascript:
http://battletech.hopto.org/html_tutorials/borderimages_javascripted/template.html
That shows it being used for glow/shadow, drop-shadow, and rounded corners.
This page:
http://battletech.hopto.org/html_tutorials/eightcorners/corners2/template.html
Shows another approach to building the image in action. Fast loading, single image file well under 1k, etc, etc…
The directory is unlocked so you can look at any files you want directly:
http://battletech.hopto.org/html_tutorials/eightcorners/
It’s really the best way I’ve found to go about it. Doesn’t fit what you were asking for - but there is no simple easy silver bullet for that effect that you can actually trust.