//with prototype.js library
Event.observe(window, 'load', changeBrowserSize, false);
window.onresize = changeBrowserSize;

function changeBrowserSize(){
	if (document.documentElement.clientWidth) {
		gbs = document.documentElement.clientWidth;
	}
	else if (document.all) {
		gbs = document.body.clientWidth;
	}
	else {
		gbs = window.innerWidth;
	}

	sbs = (gbs<=900)?'two_column':'three_column';
	document.body.className=sbs;
};