you are seeing this because you are currently viewing a normal page. to use this feed correctly, you must add ?standalone=true to the url, so it doesn't show dnn stuff or html. note that you can put the feed on an own page and then link to it (with ?standalone=true) or you can also auto-use it by using the normal blog-page and where you would usually see things like /tag/something replace with /feed/all?standalone=true