It's nothing to worry about Karl, it's just Chrome's way of telling you that you are viewing an http page as opposed to an https one.
For me in Chrome, when I'm on an http page, the http doesn't appear in the address bar, whereas the https does if I'm on a secure page.
Its fairly easy to overlook the absence of a 's' in a web address when viewing a webpage, so I feel it's better to have the more obvious difference between the words Not secure and https, compared to the difference between between http & https.