404. That’s an error.
The requested URL /add?feedurl=http%3A//www.mathexpression.com/free-math-tutor.xml&ru=https://www.mathexpression.com was not found on this server. That’s all we know.
/add?feedurl=http%3A//www.mathexpression.com/free-math-tutor.xml&ru=https://www.mathexpression.com