var focused = null;

function WriteMenu(id)
{
	document.open();
	document.write('<menu class="study">');
	document.write('<li><a href="preface.html">Preface</a></li>');
	document.write('<li><a href="letters.html">Letters</a></li>');
	document.write('</menu>');
	document.close();
}

function expan(id)
{
	if (focused == id)
	{
		document.getElementById(id).style.display = 'none';
		focused = null;
	}
	else
	{
		// close not select
		if (focused != null)
			document.getElementById(focused).style.display = 'none';
		document.getElementById(id).style.display = 'block';
		focused = id;
	}
	return false;
}

function ShowBlock(id)
{
	if (document.getElementById(id).style.display == 'block')
		document.getElementById(id).style.display = 'none';
	else
		document.getElementById(id).style.display = 'block';
	return false;
}