function disablepage(mode) {
	var shader = document.getElementById('shade');
	if(mode == 'on' || mode == 1) {
		shader.style.display = 'block';
	}
	else if(mode == 'off' || mode == 0) {
		shader.style.display = 'none';
	}
	else if(mode == 'auto') {
		if(shader.style.display == 'none') shader.style.display = 'block';
		else shader.style.display = 'none';
	}
}

function centerelement(elem_id) {
	//assuming already positioned from stylesheet
	var winH, winW, objH, objW;
	var elemObj = document.getElementById(elem_id);
	var winObj;
	
	if(window.innerHeight) {
		winH = window.innerHeight;
		winW = window.innerWidth;
	}
	else if(document.documentElement.clientHeight) {
		winH = document.documentElement.clientHeight;
		winW = document.documentElement.clientWidth;
	}
	else if(document.body.clientHeight) {
		winH = document.body.clientHeight;
		winW = document.body.clientWidth;
	} else {
		//craaaaap... make an educated guess
		winH = 900;
		winW = 900;
	}
	
	objH = elemObj.offsetHeight;
	objW = elemObj.offsetWidth;
	
	//this is approximate... user's browser may have given WINDOW or DOCUMENT size
	elemObj.style.top = eval(winH / 2 - objH / 2) + 'px';
	elemObj.style.left = eval(winW / 2 - objW / 2) + 'px';
}