displayNewMark = function() {
	if (! document.getElementsByTagName) return;
	// passage time
	var passageTime = 720; // 新着マークを表示する期間を30日（720時間）とする
	// display mark
	var mark = '<img src="http://www.isuaaat.org//images/newmark.gif" title="New Release or Modified Article" alt="New Release or Modified Article" width="30" height="12" />';
	
	var currentDate = new Date();
	var elements = document.getElementsByTagName('span');
	for (var i=0, len = elements.length; i < len; i++) {
		if (elements[i].className == 'new') {
			var time = elements[i].firstChild.nodeValue.split(':');
			var entryDate = new Date(time[0], time[1]-1, time[2], time[3], time[4], time[5]);
			var currentTime = (currentDate.getTime() - entryDate.getTime())/(60*60*1000);
			currentTime = Math.ceil(currentTime);
			if (currentTime <= passageTime) {
				elements[i].innerHTML = mark;
				elements[i].style.display = 'inline';
			}
		}
	}
};