Hello Everyone,
I was working on a project on localhost and I opened a firebug console to see an ajax request of my project and I noticed that console show me a js request to other external site that isn't in the source code of the project:

The js file request is this:
http://ak.englishtown.com/_shared/client-tracking/1.0.2-0/standalone.js. In addition the name of the folder seems suspect; client-tracking I wonder if it is a bug in firebug or actually is some kind of backdoor. I think it may be a bug, because I replicated this in another tab and did not happened again, nor on any other site.
Regards.