On my webserver I log requests that reach it for domains that are not hosted on the server. I noticed that there are entries that appear to be trying to connect to a mobile version of the site i.e. the domain name in the log is 'm.example.com' instead of 'example.com'
The site itself is fully responsive, and so doesn't need a mobile specific version.
What is the browser expecting to do with any response from m.example.com? And should I be putting anything in the actual site to prevent the browser from attempting this unnecessary request?
For reference, the user-agent of the device that made the request is 'Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:14.0; ips-agent) Gecko/20100101 Firefox/14.0.1' so it's probably not a search bot.
Just ignore it.
The ips-agent seems to be a bot from VeriSign:
This is Verisigns ips-agent bot. What this does is index your site for verisigns Internet Profile Service. This is something that they use to provide traffic data to prospective buyers of domains that are about to be expired. Verisign is in a unique position of running the .com and .net domain name servers and knows when domains will expire. They are using this information to help sell expiring domains with traffic to bulk domain buyers at registrars such as dynadot.
"Seems to be" because the source I have is not ultimately trustable. Googling "ips-agent" leads to results about VeriSign bot though, so it does seem likely enough.
Another supportive "proof": the source of the source provides a very similar user agent as the one you provided.