My friend and I were talking about interface design and cool JQuery effects. I showed him a site I built which had a bajillion hidden divs which were displayed when the user hovers over and clicks on certain images, text and buttons.
I told him that the problem with pages that have a whole bunch of hidden content which is displayed by hovering and clicking etc is that when a user wants to print the page, what do you print? What if there are 10 pages worth of text and images (and a video)? The printed page is never going to look like it does on the screen. I know that there are CSS files for printing, but those types of pages are horrible to write them for.
My friend's answer: "It's a website. Why do people need to print it? You print word documents and pdf's. Why do you need to print a webpage? Seriously!"