var windowWidth;
var windowHeight;

function changewindowsize() {
if (window.addEventListener) {
	windowHeight = window.innerHeight;
} else {
	windowHeight = document.documentElement.clientHeight ||
	document.body.clientHeight;
}
if (windowHeight > 50) {
	windowHeight = windowHeight - 50;
}

CurrentContentHeight1 = document.getElementById('left').offsetHeight;
CurrentContentHeight2 = document.getElementById('center').offsetHeight;
CurrentContentHeight3 = document.getElementById('right').offsetHeight;

if (CurrentContentHeight2 > CurrentContentHeight1 && CurrentContentHeight2 > CurrentContentHeight3) {
	CurrentContentHeight=CurrentContentHeight2;
} else if (CurrentContentHeight3 > CurrentContentHeight1 && CurrentContentHeight3 > CurrentContentHeight2) {
	CurrentContentHeight=CurrentContentHeight3;
} else {
	CurrentContentHeight=CurrentContentHeight1;
}

if (CurrentContentHeight>windowHeight) {
	document.getElementById('main').style.height = CurrentContentHeight + 60;
} else {
	document.getElementById('main').style.height = windowHeight;
}
}