The above website allows you to send in pdf files (attached to an e-mail), returning you a - rather detailed - report about the pdf/A conformity. In my experience the report could easily inform you of errors and inform you of not passing the conformity tests, while opening the same pdf file in Acrobat Reader indicates the file is PDF/A conform.
I thought this could help out FOP users who wish to create PDF/A but don't have the means of testing the conformity. I know it's been helpful in my recent project and I saw some posts in the last few weeks about it.
It might even be helpfull to the Apache FOP developers. Though Acrobat Reader indicated a file I created with FOP 1.0 as being conform, the validation service still mentioned failure and following issues:
problem severity="warning" objectID="8" clause="p32" standard="xmp">XMP packet read-only
problem severity="warning" objectID="8" clause="p33" standard="xmp">Recommended padding is not found in the XMP packet trailer
problem severity="error" objectID="8" clause="6.7" standard="pdfa">Property 'dc:date' used incorrect value type 'simple' instead of 'rdf:Seq'
problem severity="warning" objectID="8" clause="TN0001" standard="pdfa">Recommended property 'format' for schema 'dc' missing
Possibly other validators like preflight and pdf/a manager will also stumble over these issues, while Acrobat Reader is less strict.
I hope this helps some people in their projects.