You do not install the HTML, when you install the browser it depends on the browser which version it will support and there is no other assembly that would cause a support. Because it is the browser that will render the objects that is why you install the latest version of browser to target the latest approaches in the web standards. The browser, while installing, sets up the environment and assemblies to target the web development and the HTML5 (or which ever version).
There are many other blogs that allow you to read and learn which browser supports which features; it must be noted that even latest versions of browser do not support all of the HTML5 features and lag in some CSS3 functions too and every browser has its own way of supporting the elements including Internet Explorer, Firefox, Chrome and Opera.
http://www.w3schools.com/html/html5_browsers.asp[
^] (For old browser, to support HTML5)
https://html5test.com/[
^] (HTML5 support test)
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