The HTML5 Shiv
Enable use of HTML5 sectioning elements in legacy Internet Explorer
...This includes the basic createElement() shiv technique, along with monkeypatches for document.createElement and document.createDocumentFragment for IE6-8. It also applies basic styling for HTML5 elements for IE6-9, Safari 4.x and FF 3.x. HTML5 Shiv is maintained by Alexander Farkas, Jonathan Neal and Paul Irish, with many contributions from John-David Dalton. It is also distributed with Modernizr. Include the HTML5 shiv in the <head> of your page in a conditional comment and after any stylesheets. HTML5 Shiv works as a simple drop-in solution. In most cases there is no need to configure HTML5 Shiv or use methods provided by HTML5 Shiv.