To install Modernizr, download the file from this page. Then, on your site’s head tag, add a link to the file. For example:
?1<script src="js/modernizr-1.0.min.js"></script>
The second step is to include on your html tag a class of “no-js”:
?1<html class="no-js">
Why add this tag?
Because that will be the default state of the page. If JavaScript (js) isn’t on, then Modernizr won’t work at all (and probably other features of your site won’t work either…), so it’s good that we have a fallback for that case.
If JavaScript is indeed enabled, once that page is loaded on the browser, that class will be replaced dynamically and it may look something like this:
?1<html class="js canvas canvastext geolocation rgba hsla no-multiplebgs borderimage borderradius boxshadow opacity no-cssanimations csscolumns no-cssgradients no-cssreflections csstransforms no-csstransforms3d no-csstransitions video audio cufon-active fontface cufon-ready">
"There is a tool that came to make our lives as progressive web designers a bit easier: Modernizr. In this short tutorial, learn how to apply this handy script to maximum effect on your sites."