w3c/manifest — pull request #175 by mounirlamouri (2014-04-07 23:49:13+00:00)
Title: Reporting the error SHOULD be done via a UA specific way.

Also, adding that "it MAY ignore" is not that useful given that SHOULD or MAY already implies that it is possible to ignore.

It think SHOULD is better here because unless the UA has a good reason, it should do it.