Looked at the demo: it makes a total mess all over my history stack.<p>If you're trying to be "trend and geek," build a system that doesn't break the back button. Unless you're building a CSS3-only engine, you don't have to store the state in the URL. You can still parse the URL fragment to allow people to deep link the slides, having a small "link to this slide" button is worth it not to have to force the user to click back 20 times to leave the presentation.<p>Although I guess if you're using the TOC to navigate the slides non-linearly it could be considered a feature.