What happens when there's a new version against old one?

Question

when a website designed with specific version of language and after some time its new version is out and implemented by most browsers? does it is built again or something else??

Answer 1

it still supported the old one, but it will miss some key feature from the new version.

Answer 2

in general, when a new version is available, the old code still run. But there is a deprecation process of old functionalities