Haha! I did it! 90s Derpibooru in Internet Explorer 4 on Windows 95!

Ok, I may have cheated a tiny bit.
The website can't be opened by such an old browser, so I took a screenshot of the site and uploaded it on Imgur. I actually did open that screenshot in IE4 on Win95, though, that's real.
The address bar still shows an entered address even if it doesn't load, so inputting "derpibooru.org" after opening the screenshot was no problem.
The taskbar entry showing "Homepage — Derpiboo…" also is real, though not quite. Since the actual page doesn't load and thus doesn't display its title in the taskbar, I opened a Google search for "Homepage — Derpibooru", which results in a title of "Homepage — Derpibooru — Google Search" that Windows helpfully cuts off.

Unfortunately I had to do some minor image editing, after all. I had to remove the taskbar entry of the screenshot saying "http://i.imgur…" and replace the corresponding title bar at the top with "Homepage — Derpibooru" from the search (after removing "- Google Search").
For a 100% editing free picture, I guess I could have hosted a simple website displaying the screenshot and using the correct page title somewhere… Is GeoCities still around?

Fun fact: I did this while listening to canyon.mid and other classic tunes.