As a prelude to some major back-end renovation I'm planning for The Twaddle, I decided to see if I could get Internet Explorer 6 to display this XSL-ified weblog nicely, not accounting for IE-unsupported CSS (which is already taken care of at The Twaddle). Previously, IE displayed the DOCTYPE declaration as plain text at the top of the page; using strategic HTML commenting, I've managed to prevent it from doing so.
Actually, I bet simply removing the DOCTYPE declaration wouldn't affect either Gecko or IE's rendering of the page, as I think XML kicks both of them into standards mode anyway.
The next step is to try this with some of The Twaddle. And I'd probably best check Opera's effort, too.