Modernizr is a script that will detect native CSS3 and HTML5 features available in the current UA and provide an object containing all features with a true/false value, depending on whether the UA has native support for it or not.
In addition to that, Modernizr will add classes to the
element of the page, one for each cutting-edge feature. If the UA
supports it, a class like
cssgradients will be added. If not,
the class name will be
no-cssgradients. This allows for simple
if-conditionals in CSS styling, making it easily to have fine
control over the look and feel of your website.
Modernizr is dual-licensed under the BSD and MIT licenses.
Run the library: http://modernizr.github.com/Modernizr/output.html
Run the test suite: http://modernizr.github.com/Modernizr/test/