John Gruber tells it like it is about standards compliance:
If Daring Fireball looks like shit in your browser, you’re using a shitty browser that doesn’t support web standards. Netscape 4 and Internet Explorer 5, I’m looking in your direction. If you complain about this, I will laugh at you, because I do not care. If, however, you are using a modern, standards-compliant browser and have trouble viewing or reading Daring Fireball, please do let me know.