From the link I gave you first:
"That IP belongs to a website monitoring service (type in your browser's address bar). Are you using any script/service they provide?
You would have GETs with 200 response in general log when someone types one of your IPs directly in their browser. The index file from /usr/local/apache/htdocs is served. You can alter this behaviour if you like, depending on how you are using you server. "
The machine having the IP from your log seems down at the moment, but if you see repeated lines like those, try nmap, ping or nslookup to see who they are.
430, 532 et. al aren't codes.