HTMLValidator is a desktop application that validates web pages.
Making your webpages compliant with the standards means that your pages will work more reliably. Correctly written webpages are also a key step towards making your sites accessible for the widest range of users.
HTMLValidator makes validation simple, reliable and repeatable. And it works without connecting to the internet, which means your pages and content don't escape from your network (until you want them to, of course).