title: Modernizr with border-radius, media queries etc
body: <p>I've recently looked at Modernizr and have read the documentation however a few things seem a little unclear to me. It appears from reading the documentation that Modernizr is primarily used to detect if certain things are available in a browser or not, for example border-radius, media queries etc. Does it fix these things to render as expected on older browsers?</p>
  
  <p>I read in the documentation about Polyfills but I am not exactly sure on how I would implement these to add rounded corners to a div on browsers that don't support them for example.</p>
  
  <p>In addition, can Modernizr be used to allow media queries to work in older browsers or again is it simply a way to detect if media queries can be used or not.</p>
  
  <p>If it is solely a detection tool then why is it so useful? I know already that I can't use media queries or border-radius on older versions of Internet Explorer for example. If it is not solely a detection tool, then how can I use it to add newer functionality in older browsers?</p>