I have recently downloaded an app I have been looking for, for quite some time. It basically spiders a website and shows references to dead links, pages etc: http://home.snafu.de/tilman/xenulink.html.
I am finding this very useful for quality assurance of the websites we publish.
I was wondering if anyone uses a application that spiders a site like this, but also checks things such as missing ALT tags, accessbility issues and valid xHtml code.