Comment by dwaite

Compatibility is broken constantly on the web, but it is forward compatibility. This is why most browsers now auto-update to newer versions. Websites then require new features which will result in older browsers being non-functional.

Backward incompatible changes happen - they are more difficult due to lack of communication with/pressure on the sites they will break, and coordination of strategy with other browser vendors. This can actually be quite frustrating, as each browser has their own 1-3 month cadence for new releases and it is difficult to track whether a breaking change is going to land on any given browser soon enough to coordinate a new version of a site.