[wwweston]

What I've been trying to figure out for years is when/why content-box would be a desirable state of affairs.

Most of the time, you know the border-box width (and probably the padding and border) want the browser to figure out the content-width, which is why the standard box model always seemed like a pain, because it makes you do that instead (assuming you're using units where that's even possible).

I'm trying to think of a situation where that'd be useful -- where it'd be helpful from a layout perspective to start with content-width -- so I could figure out what the w3 folks were thinking, but I've always had trouble with that. Has anybody figured this out?

[yogo]

I'm guessing some of that could be due to taking the wrong path initially then leaving things the way they are. Platforms like WPF/Silverlight fixed these headaches years ago right from their conception.

[usablecode]

probably they wanted to go against IE as a behavioural pattern :)