Modernizr

Modernizr is a JavaScript library that tells you what HTML, CSS and JavaScript features are present in your user’s browser. This helps you to respond better to your users’ browser features and offer a more tailored experience.

Differences in users’ browsers and devices can often cause differences in user experience when opening your web page. To provide a consistently great user experience, you need to be able to respond to your users’ browser features in the best way. Modernizr detects the specific feature sets in each browser so you can easily deliver a tiered experience to users: using the latest features available for modern browsers while still supporting older ones.