Please modify http://cdn.sstatic.net/robots.txt to allow the Internet Archive's crawler, ia_archiver
.
Pages that were archived a few years ago include their stylesheets and appear correctly:
Pages that were archived more recently do not include their styles -- robots.txt does not allow it.
Because it doesn't use the CDN, MSO is still archived correctly:
Related: Jeff's post suggesting that people use Archive.org to archive posts.