We have a IIS7 server and regularly create reports of visitor stats using 'Weblog expert lite' anayliser and the IIS log files.
Gradually over the last month of IIS logs were getting increasing percentage of users with Browser : 'other' and OS 'other'
Looking at the IIS logs there a number of GET requests without a browser defined - instead there is a dash '-' for example:
ET /pages/VSearch.aspx - 443 - 222.333.444.444 HTTP/1.1 - ASP.NET_SessionId=f443434bs155erk0op55 - toast.pancake.org 200 0 0 21282 183 998
IIS 7 server 2008R2....
When I navigate to the site in IE11/Chrome/Firefox I can see it recognises my browser verison - any ideas what could be causing this?