HTML5 is the long-awaited next generation of HTML since the previous version that came in 1999 and i personally think it is the next best thing.
In this version of HTML, new features and new elements are introduced to help Web application authors in producing a rich user experience.
HTML5 is still a work in progress, and now (date of publishing this post) it is in the “Last Call” phase, and W3C reaffirms its expectation that HTML5 will be a W3C Recommendation in 2014. However, most modern browsers have some HTML5 support. A number of features are already in use, in a various scope of implementation. One can use HTML5 today, knowing the existing limitations and using fallback mechanisms, like modernizr.
HTML5 is not only new elements and updated markup, and it is not a One Big Thing; it is a collection of individual features, thus can’t simply detect “HTML5 support,” because that doesn’t make any sense and because all browsers support HTML5 in the general sense. But what you can do is detect support for individual features, like canvas, video, or geolocation.
In order to start having a HTML5 website or web application, you don’t need to relearn things you already know. If your web application worked yesterday in HTML 4, it will still work today in HTML5.
“Upgrading” to HTML5 is as simple as changing the doctype. The doctype should already be on the first line of every HTML page. Previous versions of HTML defined a lot of doctypes. But in HTML5, there is only one simple “single word” doctype:
after this simple tweak, you are set and ready to go. your webpage is now in HTML5. and you can make all your web pages HTML5 compatible (by setting the doctype as above) without having to use any of the HTML5 features since upgrading to the HTML5 doctype won’t break your existing markup, because all the tags defined in HTML 4 are still supported in HTML5.
So having upgraded your pages to HTML5 won’t cost you a thing, on the contrary it is of added value, because having done so it will allow you to use — and validate — new semantic elements like