When there is no standard there is no same approach for same things and we have chaos.
But we have standards for HTML and CSS, we can find them all on W3C pages http://www.w3.org/MarkUp/ and http://www.w3.org/Style/CSS/.
And still we hear from users “Why does my website look different on different browsers?” or “I want to kill developers of Internet explorer” from web-developers.
complexity of standards
First problem is the complexity of standards that should take into account many different things. It’s hard for developers to understand and develop products appropriately.
As W3C can’t simplify standards it should put special effort to develop and provide special set of test-cases like famous set of Acid tests but it should provides not just set of randomly picked features but complete cover of specifications – XHTML, CSS, DOM, SVG. There will be standard way to test browsers and someday we will finally have same picture on all browsers.
The problem not only in the standards but in human nature that incite some people to use evolving versions of HTML/CSS to get fantastic features. But I believe when W3C begins to provide tests it will be evident for anyone that developer is guilty for bugs or using of experimental features.