ignore w3c validator errors by type?

[jm3]

is is possible to pass an options hash to validator to filter out errors that aren't relevant to your use case?

e.g. if I don't care about missing alt attributes on <img> tags, can I ask w3c_validator to ignore errors of type `Required attribute 'X' not specified'?

[doc75]

@jm3 indeed, at the moment the new validator (NuValidator) does return only error message, not error numbers. Therefore it is a little bit more complex to handle.
Not sure how this can be done easily.