I was watching Dan Cederholm talk about Hand Crafted CSS, and the 4th point he made was about when validation matters.
He basically described that validation is helpful for checking why the site isn’t loading the way you want. So it’s useful for finding markup errors like close tags. Fair enough, if you are still writing HTML by hand, but a tool like HAML completely (or as close as possibly) protects you from markup errors like close tags. It also happens to make writing html twice as fast or more (just add a tag at the top and indent and you have wrapped a whole section or code.
So here’s the analogy I came up with to explain to my wife:
If I were laying railroad track, and using old wooden rail ties, I’d want to measure the width of the track every time I went to drive in a new spike, because obviously if the width of the track weren’t standardized, trains would fall right off. Using HAML* is a bit like ordering pre-cast concrete railroad ties, and instead of having to measure each time, I just have to line the track up into the groove, and bolt it down.
The only time I might run into a problem is if someone ordered rail ties for the wrong standard, which would be a bit like if you used a poor or broken HAML interpreter. On the plus side, with HAML—as opposed to railroad construction—fixing the interpreter can be done retroactively if needed.
So we really shouldn’t need to waste time building an XHTML structure validator for HTML5, because we shouldn’t be hand coding HTML5 the way we used to. But those are just my 2 cents.
Still, the video worth definitly worth watching, I’m at the very least, going to load more of my pages without images and see what happens
Or Markdown, or LaTEX, though I think HAML gives the right mix of craft (you can still control tag names, and even use HTML5y tags) and markup detachment (you don’t have to worry about syntax, and if you mess it up, it shows up right away on an error page), but you already know it, if you know HTML.