NCSA Mosaic is widely regarded as the first web browser. It was what the first Microsoft Internet Explorer was based on back in the 1990s.
One of the key points of HTML is that webpages if they're done well should gracefully degrade so the features that aren't supported by the web browser should just not be shown. Obviously for many webpages that rely heavily on javascript that's impossible, but I was pleasantly surprised by the HTML that lotide kicks out and I wanted to test the hypothesis.
As you can see, the basic fundamentals of the webpage work just fine in a degraded state. Obviously there's some issues I think are related to unicode, but considering it's running on a win16 web browser first developed in 1993, I'm pretty impressed it loads in a meainingful way at all!
(Shout out to otya128 for developing the winvdm upgrade that allows the latest windows 10 to run win16 programs, I used that to load mosaic)