The Web is changing all the time. From a technical perspective, more functions are added, which opens doors to new possibilities. From a developer perspective though, it is getting more expensive to test web pages in all browsers. Before, when Internet Explorer had more users, it was worth to only check the page in IE and still make it available for most of the web users. Now, when all old/new minor browsers are getting big, you cannot be sure that all will view the page as you want to. That means that more time is needed to make a page compatible for all browsers.
HTML5 – which should not be platform or web-browser based, is shown differently depending on web-browser, web-browser version and platform. With other words, a page on, for instance, windows using Firefox, would not be displayed the same on a Firefox browser on Android.
The big issue with all kinds of web-browsers is that more time is needed to test a project, which might be expensive. Once again, if a project is to be tested in all web-browsers, it may cause project delay, or, to solve the first issue of time, it might require more web-developers, tester, which might therefore cost more.
I do not think that this issue may be solved in the nearest future, because we are getting more and more devices, such as smartphone, tablet-PC, TV, et cetera. Everything listed has an pre-build web-browser. In the current situation, we cannot take it for sure, that the web-page will be displayed correctly on all devices.