Many years ago someone posted a really cool link on this site. I suspect the odds that the poster will read this and remember the link are close to 0, but I figured I'd give it a shot.
The link was to a site that you needed to advance from one page to the next. I think there were a total of 20 or so pages.
The way it worked was you figured out the clue on the current page and moved on... Let's say on the first page there was an image. If you clicked that image you'd go to the second page. Then on the second page there was nothing, but if you viewed the source you'd see a link for the third page.