Message
Undefined foo element: bar
Explanation
Your feed contains an element that this validator does not recognize.
Solution
This may just be a typo. Element names are case-sensitive; make sure you're using the right case. For example, pubDate has a capital "D"; textInput has a capital "I".
If you were really trying to include a new element that you have defined, you will need to put it in a namespace.
Not clear? Disagree?
Let us know on the feedvalidator-users discussion list!
