Apple already made clear that it was expanding iOS 5-like notifications to the desktop with OS X Mountain Lion, but it now looks as though that's extending to your web browser, too. Some visitors to iCloud.com have reported seeing notifications show at the top of the page that were both based on iOS' look and which were clearly not ready for prime time -- not unless Default Title for English is a new iCloud feature, at least. There's no indication of how advanced notifications might become in Apple's web portal, or if they'll transition from development cocoon to public butterfly at all. In the meantime, though, keep an eye on the top of your browser and let us know if you see anything leap out in the near future.
Apple OS X Mountain Lion
Apple OS X Yosemite