Hello!
If you've come here from www.456bereastreet.com you should be aware of what this page is for.
All data and pathing issues are now resolved, yipeee!
Here's the real page, as it currently appears in the site: links.html.
I'm off to work on the graphics now, which are a little rough for my taste.
If I ever get time I'll write a guide here on how to use this technique, demonstrating a few nice possibilities for it and giving away a load of corner and border png/gif sets.
Yeah, like I'll ever get time to do that!
A man can dream....

From the CSS Mastery book downloaded CSS file:
.bb {
background:url(box.png) no-repeat 100% 100% !important;
background:url(box.gif) no-repeat 100% 100%;
margin:0 0 0 12px;
height:14px;
}
.bb div {
height:14px;
width:12px;
position:relative;
left:-12px;
background:url(box.png) no-repeat 0 100% !important;
background:url(box.gif) no-repeat 0 100%;
}

From 456BereaStreet CSS (v2):
.bb {
height:14px;
margin:0 0 0 12px;
background:url(box.png) no-repeat 100% 100%;
}
.bb div {
position:relative;
left:-12px;
width:12px;
height:14px;
background:url(box.png) no-repeat 0 100%;
font-size:0;
line-height:0;
}

From post 72. on 456BrereaStreet:
.bb {
height:17px;
margin:0 0 0 18px;
background:url(/box2.png) no-repeat 100% 100%;
}
.bb div {
position:relative;
left:-18px;
width:18px;
height:17px;
background:url(/box2.png) no-repeat 0 100%;
font-size:0;
line-height:0;
}

From this page's CSS, as above but tidier (I recommend this version):
.bb {
height:17px;
margin:0px 0px 0px 18px;
background:url(/images/custom_cornered_box_images/box_black_1.png) no-repeat 100% 100%;
}
.bb div {
position:relative;
left:-18px;
width:18px;
height:17px;
background:url(/images/custom_cornered_box_images/box_black_1.png) no-repeat 0% 100%;
font-size:0px;
line-height:0px;
}

Note how, by this point, the units of measurements are all given, and in a consistent manner.
This avoids any wierd issues that will otherwise cause you headaches) and we no longer need a gif version.
Roger Johansson at www.456bereastreet.com has info on that, though I prefer a HTC trick to enforce png support in older versions of Explorer.
See source code for this page and use Firefox's brilliant WebDev add-on tool to grab the code for the htc.
A similar tool is available for Explorer but this is less reliable. Read more.
tom barnfield, www.runninghead.com