function dynamicLayout(){
	var browserWidth = document.viewport.getWidth();

	//Load Thin CSS Rules
	if (browserWidth <= 800){
		changeLayout("thin");
	}
	//Load Default CSS Rules
	if (browserWidth > 800){
		changeLayout("default");
	}
}

// changeLayout is based on setActiveStyleSheet function by Paul Sowdon 
// http://www.alistapart.com/articles/alternate/
function changeLayout(description){
   var i, a;
   for(i=0; (a = document.getElementsByTagName("link")[i]); i++){
	   if(a.getAttribute("title") == description){a.disabled = false;}
	   else if(a.getAttribute("title") != "default"){a.disabled = true;}
   }
}

Event.observe(window, 'load', dynamicLayout);
Event.observe(window, 'resize', dynamicLayout);