function footerposition() {

	//ウィンドウの高さ
	var windowHeight = document.all ? document.documentElement.clientHeight : window.innerHeight;

	//各部の高さ
	var headerHeight = document.getElementById('header').clientHeight;
	var boardHeight = document.getElementById('board').clientHeight;
	var contentHeight = document.getElementById('content').clientHeight;
	
	//フッタ部の高さ
	var footerHeight = document.getElementById('footer').clientHeight;

	var fitHeight = windowHeight - headerHeight - boardHeight - footerHeight;
	if ( fitHeight > contentHeight ) {
		contentHeightStr = fitHeight + 'px';
	} else {
		contentHeightStr = contentHeight + 'px';
	}
	document.getElementById('content').style.height = contentHeightStr;

}



window.onload = function() {
	footerposition();
};



window.onresize = function() {
	footerposition();
};