// via http://github.com/hatena/hatena-bookmark-xul/blob/master/chrome/content/common/05-HTMLDocumentCreator.js
function createDocumentFromString(source){
	var doc;
	try {
		doc = document.cloneNode(false);
		doc.appendChild(doc.importNode(document.documentElement, false));
	} catch(e) {
		doc = document.implementation.createHTMLDocument ?
				document.implementation.createHTMLDocument('hogehoge') :
				document.implementation.createDocument(null, 'html', null);
	}
	var range = document.createRange();
	range.selectNodeContents(document.documentElement);
	var fragment = range.createContextualFragment(source);
	var headChildNames = {title: true, meta: true, link: true, script: true, style: true, /*object: true,*/ base: true/*, isindex: true,*/};
	var child, head = doc.getElementsByTagName('head')[0] || doc.createElement('head'),
	           body = doc.getElementsByTagName('body')[0] || doc.createElement('body');
	while ((child = fragment.firstChild)) {
		if (
			(child.nodeType === doc.ELEMENT_NODE && !(child.nodeName.toLowerCase() in headChildNames)) ||
			(child.nodeType === doc.TEXT_NODE &&/\S/.test(child.nodeValue))
		   )
			break;
		head.appendChild(child);
	}
	body.appendChild(fragment);
	doc.documentElement.appendChild(head);
	doc.documentElement.appendChild(body);
	return doc;
}