Better HTML5 & CSS3 Usage By Detecting Browsers Capabilities With Modernizr
Similar to the IE6 situation, when using HTML5/CSS3 in our websites, it is a good idea to offer non-problematic outputs to web users with older/non-standard browsers.
Also, Modernizr adds support for styling HTML 5 elements. This allows you to use more semantic, forward-looking elements such as
<dialog> without having to worry about them not working in Internet Explorer.