With us moving continually closer to HTML5 in terms of adoption, is writing HTML for validity something the web is rejecting, allowing us to straddle standards as the web continues to be in a perpetual state of transition to the "next" thing?
Is validation important?
Validation will always be important, but during times of transition from one standard to another it's very difficult to pull off. It's especially hard when the standard isn't even finalized and agreed upon yet. So while validation is important, business is more important and simply won't wait for validation. So there will inevitably be some indefinite transitional period where validation will be summarily discarded in many cases until a more stable standard is reached and implemented that can provide a reliable basis for validation.
Html5 is "out", but it isn't set to be finalized until 2014 sometime.
HTML validation isn't a huge deal deal for a few reasons, that don't really have anything to do with HTML 5.
HTML 4.01 Strict Validation is one of my automated tests in my ATDD test suite.
For us validation is important because of consistency of browser behavior. So if you don't need consistency of behavior across different browsers (and browser versions), then it's probably more of a nice-to-have.
Driving consistency of behavior for all your pages makes the following cheaper:
For once, Google penalizes websites with HTML errors, not sure how much.
They do the same with slowly loading pages, and HTML rendering is a CPU extensive task and doing something incorrectly forces the browser to "guess" the correction, this slows down the page rendering time and even worse browsers often guess wrong.
As a page gets complicated by other dynamically inserted elements with invalid HTML, chances that whatever was detected/ignored by the browser will now becomes in effect, and that cost more to fix than initially considering validating HTML.
