Different browsers are at different stages in supporting new features as they are released.
The site caniuseit.com collects all the information about which CSS features are supported on the various browsers.
For instance, a fairly new CSS feature, the grid, is not yet fully support across all browsers, but is almost there. It is a widely popular feature among developers, as it makes the layout of web pages much easier, but developers need to be aware of whether the browser their target customers are likely to be using will support it.
