Most of the users complain that when you click on that, it does not work.

Yes, It wont work till all the browser manufacturers support that.

what is it anyway ?
Have you seen a mailto: added to links to the email addresses? It is for opening a mail compose window on your email program automatically when you click on those links. Browsers understand this keyword mailto and acts accordingly.

Similarly, W3C (World Wide Web Consortium) is suggesting to have feed: to be added to the feed links, so anytime the user clicks on it, the browser can launch the feed reader program(if it is installed on that machine) automatically.

It won’t work as of now, because not all browsers are made to understand this tag.
Till they upgrade, you can safely remove this feed: part from your feed links.

[Reposted from one of my other sites]