How to detect if browser is below IE8?

I hate IE, I only want to display an out-of-date browser notification to IE8 IE7 IE6 IE5.5 etc. users on my site :)

I want 开发者_JAVA百科to detect if browser version number is below IE8. I am open to Javascript, HTML, PHP, jQuery. How could I do this?

You can use this mark-up in your HTML:

<!--[if lt IE 8]>
<p>You aren't using a recent version of Internet Explorer.</p>
<![endif]-->

Reference.