window.onscroll = function()
{
	// Thanks to Johan Sundström (http://ecmanaut.blogspot.com/) and David Lantner (http://lantner.net/david) 
	// for their help getting Safari working as documented at http://www.derekallard.com/blog/post/conditionally-sticky-sidebar
	if( window.XMLHttpRequest ) { // IE 6 doesn't implement position fixed nicely...
		if (document.documentElement.scrollTop > 150 || self.pageYOffset > 150) {
			$('content_sub').style.position = 'fixed';
			$('content_sub').style.top = '0';
		} else if (document.documentElement.scrollTop < 150 || self.pageYOffset < 150) {
			$('content_sub').style.position = 'absolute';
			$('content_sub').style.top = '0';
		}
	}
}