function open_comment(){
	var box = document.createElement('div');
	box.id = 'comment';
	box.style.width = '320px';
	box.style.margin = '0';
	box.style.padding = '10px';
	box.style.border = '1px solid gray';
	box.style.backgroundColor = '#FFFFFF';
	box.style.color = '#000000';
	box.style.textAlign = 'center';
	var form = document.createElement('form');
	form.style.margin = '0';
	form.style.padding = '0';
	var textarea = document.createElement('textarea');
	textarea.name = 'comment';
	textarea.style.width = '280px';
	textarea.style.height = '80px';
	var button = document.createElement('input');
	button.type = 'button';
	button.value = '送信';
	button.style.width = '280px';
	button.onclick = function(){
		textarea.disabled = true;
		button.disabled = true;
		var ajax = new XMLHttpRequest();
		ajax.onreadystatechange = function(){
			if(ajax.readyState == 4){
				if(ajax.status == 200){
					var ok = false;
					var xml = ajax.responseXML;
					var ret = xml.getElementsByTagName('return');
					for(var r = 0; r < ret.length; r++){
						if(ret[r].firstChild.nodeValue == 'OK'){
							ok = true;
						}
					}
					if(ok){
						box.parentNode.removeChild(box);
					}else{
						alert('ERROR: 送信失敗！');
					}
				}
				textarea.disabled = false;
				button.disabled = false;
			}
		};
		ajax.open('POST','http://scheme-users.jp/cgi-bin/comment.cgi',true);
		ajax.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
		ajax.send('comment=' + encodeURIComponent(textarea.value));
	};
	form.appendChild(document.createTextNode('Comment:'));
	form.appendChild(document.createElement('br'));
	form.appendChild(textarea);
	form.appendChild(document.createElement('br'));
	form.appendChild(button);
	form.appendChild(document.createElement('br'));
	box.appendChild(form);
	document.getElementsByTagName('body')[0].appendChild(box);
	box.style.position = 'absolute';
	box.style.left = document.documentElement.scrollLeft + ((window.innerWidth - box.offsetWidth) / 2) + 'px';
	box.style.top = document.documentElement.scrollTop + ((window.innerHeight - box.offsetHeight) / 2) + 'px';
}
function comment(){
	var comment = document.getElementById('comment');
	if(comment){
		comment.parentNode.removeChild(comment);
	}else{
		open_comment();
	}
}