Since new web browsers are being released all the time, the number of different browsers that people can use to access the web is constantly growing. The one thing that we can't do though is to design our web pages so that they work identically in all browsers. Were we to do that then our pages would by necessity consist of nothing but plain text laid out sequentially down the page with an occasional link. That's because that is all that some of the earliest web browsers support.
More modern browsers support more features and as the browsers that support these newer features have been adopted the people writing web pages have incorporated those new features. After all why bother having new features i web browsers if you are not going to take advantage of those features for the browsers that support them. The only thing that really needs to be considered with respect to the older browsers is to make sure that your web page is still usable in those browsers (even if that means that your page appears to consist of nothing but plain text laid out sequentially down the page with an occasional link in those browsers.
Since you are always going to have at least some people using browsers that don't support all the features you build into your page the only affect that using the most modern of features that any browsers support will have is to increase the number of people using browsers where they will not get to see all the features. There is nothing wrong with this as by incorporating features into your page that make the page work even better for those using the latest browsers means that you are doing your bit to encourage people to keep their browser up to date.
The only difference that incorporating the very latest features that browsers support into your page will make is that instead of the majority of your visitors being able to see your page exactly as intended it will only be those using leading edge browsers who will see it. While antiquated browsers such as IE7 continue to be used by a significant percentage of people on the web this means that the majority of people will see a slightly less sophisticated version of your page. Does this really matter though? Since few people other than those actually developing web pages swap back and forth between browsers the vast majority of those people will not even know that the additional features exist and if they do find out then it is one more thing o help encourage them to upgrade to the better browser.
If we keep delivering web pages that work the same for the most popular antiquated browsers as they do in all the more modern ones then what reason do those using those browsers have to upgrade to anything more modern?
The one thing to watch out for though is to make sure that the features that you add into your page are not only supported by at least some browsers (so as to be worth adding) but are also a part of a recommended standard that more browsers can be expected to adopt in the future so that over time more people will see those features in your page. One of the big problems that led to some browsers ending up so far behind in the first place related to the implementation of support for things from draft standards which never made the final version or worse yet the implementation of proprietary code in the hope that it would become popular enough to make it into the next version of the standards. Implementing such features into your page may make the page nicer for those using the specific browser that supports it but there is no guarantee that it will ever be adopted by all browsers. There are even some parts of the recommended standards which some browsers are still a long way from supporting but at least with those things there is at least the knowledge that the browsers are supposed to be working toward adding that support.
This article written by Stephen Chapman, Felgall Pty Ltd.