winint = 0;
fadeint = 0.03;
divopacity = 0;
totaldivs = 2;

function show(num) {
	if (winint) {
		window.clearInterval(winint);
	}
	for (i=0; i<totaldivs; i++) {
		document.getElementById('main'+i).style.visibility = 'hidden';
	}
	document.getElementById('main'+num).style.visibility = 'visible';
	document.getElementById('main'+num).style.opacity = 0;
	divopacity = 0;
	winint = window.setInterval(function() {
		document.getElementById('main'+num).style.opacity = divopacity + fadeint;
		divopacity = divopacity + fadeint;
		if (divopacity >= 0.9) {
			document.getElementById('main'+num).style.opacity = 1;
			window.clearInterval(winint);
		}
	},50);
}