function getWindowHeight() {
	
	return window.innerHeight ? window.innerHeight : document.documentElement.clientHeight ? document.documentElement.clientHeight : document.body.clientHeight;
}

function setWindowHeight() {

	var windowHeight = getWindowHeight();
	
	new_margin = Math.round((windowHeight - 470) / 2);

	document.getElementById('page_margins').style.marginTop = new_margin+'px';
	
	ajax_repositionTooltip();

}

function getWindowWidth() {
	
	return window.innerWidth ? window.innerWidth : document.documentElement.clientWidth ? document.documentElement.clientWidth : document.body.clientWidth;
}