MDN says border-radius was added to Chrome in 2010 and Firefox in 2011, and Chrome added the prefixed version in 2008. https://developer.mozilla.org/en-US/docs/Web/CSS/border-radi...
Firefox had it from 2006, prefixed.
IE was the holdout, not having it until v9 in 2011.
[0]: http://css3pie.com/
> I remember in the early days cobbling together elements with top-left, top-right, etc image slices. Want't really too long ago.. maybe 10 years?
To me this is core ajax and php era, so ~2002-2006 which would be about 18 years ago.
By the time CSS standards for rounding corners arrived a lot of pain has been inflicted on us developers, but by now it feels as if this era never existed (same with pre/post flex to take another CSS milestone)