If using the Chrome web browser, then the ‘this XML file does not appear to have any style information associated with it’ message is the standard thing you’ll see. Google removed support for RSS and their reader tool, when they launched the Google+ service a few years back (the two services rivaled each other). I don’t know if it’ll ever be fixed; it seemed like a bit of a knee-jerk reaction at the time.
In past projects where a client has wanted people to subscribe to their website RSS feed, we’ve usually done it in two stages with a modal window. Firstly the website visitor clicks a button in a sidebar marked ‘subscribe to our RSS feed’ or similar. That opens the modal window (popup) and displays some basic information about what RSS is, recommended tools / links and provides the RSS link in an input box, that the website user can click and copy. We’ve normally given the instructions for people to copy that link into their email software or a free RSS reader like Digg.
Honestly, I think the days of being able to click a link and instantly subscribe to an RSS feed from a web browser are largely gone. Chrome has dropped it, IE does some funky stuff and I suspect Safari on iOS handles things differently too in absense of a native RSS reader. RSS is still an important service in some websites for some users, but you kind-of have to build the RSS subscription system into your site documentation and tell visitors how to use it.