From
WotC's Site:
"For the D&D website, we’re planning a horde of content to coincide with Fiendish Codex 1. For starters, R&D came to the website team with a request; while the FC1 sourcebook contains a number of demon lords (just take a look at the Table of Contents to find out which ones), R&D wanted a fair representation of their aspects. These will appear on the website throughout the month – 11 aspects in all.
Material cut from the sourcebooks due to space considerations often make ideal web enhancements; unfortunately, not every book has this available. This month, however, we have been given such “cutting room floor” material for FC1—including a new monster, a new detailed abyssal layer, and several short layer descriptions. Plus, we’ll offer a look at the artwork of D&D’s demons throughout the editions, tactics & tips for combating various demonic foes, and even more specialized half-fiend templates."
That last paragraph gets my heart all a'flutter.