Yesterday one of my colleague raised a query on "Site Level Warnings" in Sharepoint 2007 content databases (actually this is the warning site level, check the content database in application management in Central Admin of MOSS 2007). So i tried to do some research on this and till then one of my other colleague Kenny got us an answer that it logs the warning inside the "Event Log" and the message looks something like: "The content databases have exceeded the Warning web site count. Either change the content databases website capacity settings or add more content databases.".
This is the same way as it used to be in old WSS v2 (SPS 2003) days. So the site level warnings are posted on the server Application event log.