w3.org feed validation service is provided at http://validator.w3.org/feed/. It offers you two methods to validate your feed document:

► Validate by URL - Validating a feed file by entering the URL where the feed file is located.

► Validate by Direct Input - Validating a feed file by entering the content of the feed file. But this method is not working at this time.

If you want to the w3.org feed validator, you can follow the tutorial exercise below:

1. Go to http://validator.w3.org/feed/.

2. Enter http://rendc.org/atom.xml into the Address field and click the Check button as shown in following picture:

W3 Atom Feed Validator

3. You should see the validation result page with a "Congratulations" message.