The browser landscape is a complicated one. Sometimes, a new feature will be accepted as standard and will be implemented in most or all browsers very quickly, but this is not always the case. Some features can appear in one browser and go through many iterations before a standard is agreed upon and they are implemented elsewhere.
For example, CSS Flexbox, which you learned about in Chapter 2, Structure and Layout, first appeared way back in 2009 and went through several experimental versions before a recommendation for the CSS standards was agreed upon. The browser support is now quite good, but it has taken 10 years to get there.
We, as developers, often have to work to browser specifications (that is, a list of browsers the page must support), and we may need to know whether a browser feature is available for all of the browsers included in the specification. There are several sources for this information, and one of the most palatable is the caniuse website....