Browser compatibility detection and overlay suggesting alternate browsers

I开发者_JS百科'd like to find a small javascript program which checks browsers and if the browser is < IE9, provides an nice overlay to users suggesting an alternative browser (switch to Chrome, or upgrade to IE9).

Is there something that does this that is well designed and easy to set up?

Write an overlay with HTML and CSS, and then put it in an IE conditional comment:

<!--[if lt IE 9]> (overlay code here) <![endif]-->