I was reading a blog entry from Mr Rowan Simpson (of trademe fame) about an idea he had and I think he's onto a winner...

From his site:

The problem

It is very difficult to ensure that all of the page in a large and dynamic web sites contain valid HTML, especially as changes are made to those pages over time.

...

The Solution

While developing and testing a site, or even just while browsing, we typically visit a large number of different pages.

The proposed tool will run in the background while we use the website and capture the details of each HTTP request and corresponding response. The HTML that is returned can then be validated asynchronously by the tool.

At the end of the browsing session (or even during, if required) the tool will provide a list of the pages that have been visited and a count of the number of warnings or errors contained on each. The user will be able to drill into the details of any page to investigate the cause of the warnings or errors.

This would allow developers and testers to quickly and easily validate a large number of pages, including those that require users to post form information and login, without any extra work over and above what they are already doing.

I love the idea, it would make for a fantastic firefox extension. It would be extremely useful, especially with the NZ Government Web Standards.

Actually, the more I think about it, it could make an excellent google analytics type piece of software that collected info automatically behind the scenes and kept a nice history (showing trends etc like Rowan mentions) for you to review at your lesuire.

This could potentially put alot of additional stress on a site, but if its done right...

Unfortunately, like Rowan, I don't have that sort of spare time on my hands either! :-/ I'd love for someone to pick up the ball and run with it!