About the back button: Do other people feel the same way? This is by design, but I'm open to change this behavior if people would prefer it.
But if you've got some other keyboard navigation to go back / forward then maybe it wouldn't be so much of a loss...
Great site, it's what the official docs should be.
If replaceState was used when interacting with a section and push/pop state was used when changing states/going back then it should only take a few backs to get back to where you were.
(I'm on my phone though so it's possible there's some alternate navigation on widescreen layouts that I'm not seeing).
For example, if I open two class popups, then hit the back button twice, I'd expect to end up on the overview page with no popup open, but what actually happens is the last popup stays up even while the URL changes.
The other case is, if I have a popup open, then close it, I'd expect the URL to change to having no fragment to reflect that, but instead the old fragment sticks, so a reload would actually show the last popup you had open.
These are obviously minor things and I like the project, so I hope not to come across too nitpicky.
Also, does nobody know that in pretty much any browser, you can hold down the back button to get a history list so you can jump back multiple pages in one step? Or the "History" menu.
That being said, this is really awesome work and will certainly come in handy! Nice job.
Don't change the url when people are clicking on the urls, but have a share icon for each element that is placed in the modal that pops up when clicking on it.
In this way, url stays the same while people are checking the elements, and you can still have specific urls for each element for people to point to a specific demo if they want.
Share icon copies the url e.g "http://hackerthemes.com/bootstrap-cheatsheet#dropdown-header... to clipboard and visiting this url pops up the dropdown-header demo.
I find the back button as you implemented it handy.