Scrolling through Domain Pigeon’s log file, I see:
ActionController::RoutingError (No route matches "/MSOffice/cltreq.asp" with {:method=>:get})
What’s going on here? My first impression was that someone was probing the site for vulnerabilities, but it turns out that’s not the case. Googling points to the answer:
Is someone attempting to hack my system? No, Not really.
These are requests from a user who has installed Microsoft Office and Internet Explorer, and who has enabled the “Discuss” toolbar in his browser. When that toolbar is enabled, the browser will automatically query for these two files when visiting each site, to determine whether the Office Server Extensions are installed.
Microsoft, was there not a better way to do this?
Matt Mazur 
In Apache, I intercept calls to the Microsoft Office web pages and direct them to a web page asking the user to remove the crap from their Internet Explorer or get Firefox and think about replacing expensive Microsoft Office with free Open Office
http://www.slough.info/system/system1.php
Paul, it is great that you can afford to lose visitors or to divert their attention. All websites should do the same. I was wondering weather this call is related to a particular Office version … this post is 2009, but in 2014, the issue remains. How in earth, MS crap would simply make automatic calls to each website?! What kind of programmer is so worse to think of no alternative and just throw some random calls to an URL that probably 99.5% websites will just 404it?