About six years ago, I worked in a company where the standard desktop setup was Opera on FreeBSD. At the time, Opera's default user agent string was a contempor

About six years ago, I worked in a company where the standard desktop setup was Opera on FreeBSD. At the time, Opera's default user agent string was a contemporary version of Internet Explorer. Furthermore, Opera hadn't released a binary for FreeBSD so it was run under FreeBSD's Linux binary compatability. So, the web server thought that the client was Internet Explorer and the client thought that it was running on Linux. I was astounded by the number of websites that failed when I changed the user agent string to Opera but worked fine in the default setting. Why bother testing a user agent string if the app doesn't know which operating system is being used? Why do something adverse when the test fails? Old programming adage: never test for a condition you cannot handle.