HTML used to be a very nice format at the age of xhtml 1.1, very formally specified, and a tie with DOM was assured by vert strictly standardised DOM v3. And ACID3 was giving you a pixel for pixel repeatability during rendering.

HTML+JS today... now it's effectively a standard in name only, and Chrome is the new IE6. The standard is now "what has worked in the last stable release"

Now go to http://acid3.acidtests.org/ and see how the latest stable Chrome release can't render a decade old CSS testcase.