The invaluable epubcheck has officially been at version 1.0.3 for months, but the latest incremental build (1.0.5) has significant improvements. I’ve been seeing a number of ebooks entering the marketplace which pass epubcheck 1.0.3 but have serious flaws that are caught in 1.0.5.
At Threepress we’ve been using 1.0.5 internally for some time, as I suspect many organizations have, so I’ve upgraded the public epubcheck validation service to use the latest code. I’ll keep it up to date periodically until version 1.0.5 becomes final.
(If you prefer to use an earlier version you should download the code directly from the main site, but I strongly recommend against doing so as many serious errors may be bypassed.)