HTML5 Backwards Compatibility
Although HTML5 is supported in all modern browsers, there are issues in terms of backward compatibility, meaning if we build a website using HTML 5.0 the web pages will not work properly in older browsers starting from Internet Explorer 9.0.
There are some workarounds to modify a HTML5 website so that it will not have problem’s when viewed on IE9 due to unknown HTML elements, … just one example is to define the HTML5 semantic elements as block elements. However, this type of workaround will not work on IE8 and earlier versions.
Thankfully, Sjoerd Visscher created the HTML5Shiv! The HTML5Shiv is a JavaScript workaround to enable styling of HTML5 elements in versions of Internet Explorer prior to version 9.
The HTML5Shiv should be placed within the <head> tag, as follows.