Comment by lucb1e

Right, that sounds like a blind spot of mine as well. We test nearly only commercial products (or open source projects large enough to get commercial backing), and in private time, of course I'd come across big websites sooner than across small ones. Still, I'm surprised I never even heard of it (also considering we literally had a class on XML and the features, like these DTDs that I never found a use for in the decade since). Sounds like I should look into XSLT, since I also build a lot of small tools and simple old tech is generally right up my alley!