Sometimes you may need to develop custom tracking code for Google Analytics. If you sit in front of your development machine and the development or testing site you are using is localhost you will run into the problem that you don't see a tracking event firing to Google.
So you may ask you how to test the code without going into production? There are several options...
var _gaq = _gaq || []; _gaq.push(["_setAccount", "UA-1234-1"]); _gaq.push(["_setDomainName", "none"]); _gaq.push(["_trackPageview"]);
Personally I prefer to use variant #3 as it may be the easiest to add - at least in Drupal with the Google Analytics module as I do not need to maintain the hosts file that may collide with DNS services. Some users may also work on locked down PC's and have no permission to alter the global company DNS server configuration or their local hosts file.
Now you will see the hits to Google's __utm.gif.