You are being nagged on because your project's name showed up in the nightly Checkbot run. Checkbot checks for broken links etc. This probably means that you are either pointing to a broken link or that someone is pointing to a broken link on your site. Or something else, it check's a bunch of stuff. Update your webpages or you shall be nagged again next week.
To find out what's wrong with your webpages, please consult:
http://common-lisp.net/checkbot/checkbot-common-lisp.net.html
Any questions? You can reach the author of this cronjob at admin@common-lisp.net
Thanks!