Doesn't work on legacy HTML documents #3
Description
Specifically, it doesn't apply correctly to documents with a declared doctype that doesn't support CSS (e.g., HTML 3).
For example:
We can't reliably apply filter: grayscale(100%); if the document relies on text, bgcolor, or similar stylistic attributes used in HTML 3 or older.
Maybe provide a warning when toggling that the doctype is too old to reliably function.