As part of our functional testing, we will want to verify that all the links in the portal are valid – that they take us to other pages in the portal, and that those pages don't give us an exception incident form or some other clear indication of brokenness – and do so in an automated fashion. It would be a bonus to do HTML validation as we go.
What I'd like you to do is begin by assessing our options here. We can use a specific link checking tool, or we could write our own crawler & link checker using HtmlUnit/JWebUnit or Selenium.
I would like for whatever we choose to be practical to execute via JUnit tests, so that is one hard constraint.
One advantage of using Selenium is that it will get you familiar with that tool set which we're planning to use for more specific functional testing testing of our pages, but I want you to be free to choose something else if is compellingly better.
Once we've agreed on a tool, you can begin coding it up or setting it up as the case may be.