I found this (long forgotten) html tutorial that dates from 1996. Certainly web development for different browsers has become much easier in the last 13 years. But as @izs points out, the parting advice is still valid today:
Content is all. Yes, you want your pages to render as precisely and attractively as possible under every browser in the known universe. But your efforts will take you only so far. After that, you need to learn to just ‘let go’.