Comment by Izkata

> Box-sizing should be border-box by default.

It was in Internet Explorer, everything being misaligned because of this difference was one of the reasons it got the nickname Internet Exploder.

Edit: To be clear this was more of just a fun fact, I agree with this statement. The misalignment was because people would build to content-box without knowing it was different in IE. Worse still IIRC they acted differently even before this CSS attribute was exposed, so you had to make it work both ways if you wanted your site to look nice everywhere.