Joshua Allen has a post entitled RSS Last Mile where he complains about the lack of a clear story with regards to one click subscription to RSS/ATOM feeds. I wrote about the various approaches to achieving one click subscription to ATOM and RSS feeds a few months ago which led to drafting feed URI scheme. Three months later, one click subscription to syndication feeds is still as confused as it's always been. A lot of the major aggregators support the feed URI scheme but none of the major blogging tools has decided to support it yet. Instead a lot of folks still use the 127.0.0.1 hack popularized by Radio Userland but which is now utilized by a wide number of aggregators. However most websites just do nothing with regards to one click subscription and just have a hyperlinked image, such as , which points to the RSS feed. 

The only new thing I've seen is that yet another person has cooked up their own one click subscription scheme that is incompatible with all the others. Thanks to Joshua's post I found an RFC for one click subscription to syndication feeds which seems to me to be the least advantegeous of the approaches that have shown themselves thus far.

The author of the RFC wrote the following about existing approaches, I've annotated his comments with mine in red text

Current solutions:

• have the aggregator clients register with some mime-type (for either RSS or OPML), I don't believe anyone's actually implemented this since most aggregator authors know this doesn't work for a variety of reasons listed in my post on one click subscription to ATOM and RSS feeds
• have a new protocol (feed:), actually this is a URI scheme not a protocol, and the process is the same as the above, have the aggregator clients register with as the handler for some URI scheme
• support as many clients as possible via javascript (see QuickSub),
• transform the RSS with XSL in the browser to help newbies (no really a one-click subscription solution though).This could be a one click subscription option if the prettied up RSS feed shown to the user also displays a link that uses one of the other 3 techniques mentioned above. So this approach is really orthogonal to the others and in fact can be considered complimentary

The author of the RFC post then goes on to suggesting an Internet Explorer specific solution namely that

Replace the orange Feed button:
The orange feed button needs to be wrapped with an object tag:

<object classid="clsid:0123456789ABCDEF [1]">
  <param name="feedurl" value="http://feedurl [2]">
  <param name="description" value="blah blah [3]">
  <param name="imageurl" value="http://buttonimageurl [4]">
  <a href="http://feedurl [2]"><img src="http://buttonimageurl [4]" /></a>
<object>

If the ActiveX control with class ID [1] is installed, it displays a custom "subscribe" button. When you click on it, it uses the feedurl parameter [3] to subscribe.

Besides the fact that this approach is Internet Explorer specific since it requires an ActiveX object it doesn't offer anything that the other approaches don't.  I don't see why Joshua thinks it's a good idea, considering that all 3 of the other approaches work in a variety of browsers on a variety of platforms.