Oddities in the error log

I'm doing my end-of-month statistics, and I see in my error log that something has been trying to connect to individual entries in my weblog with mark-up in the URL's.  For example:

File does not exist: http://blog.jackvinson.com/archives/2004/03/03/<b>monster</b>_project_management.html

Of course, the url without the bold mark-up exists just fine.  Is this coming from some kind of robot?  I can almost imagine a search service that is highlighting matched words in the URL's for those files.  I note that when I get these errors in my log, there are usually several from the same IP address.  Hmm, it is almost always the same IP address.  This suggest a robot even more.