var prevblock = 'null_block';
function shb(block, close) {
	var b = document.getElementById(block);
	if (b != null) {
		if (close == true) {
			b.style.display = 'none';
		} else {
			b.style.display = (b.style.display == 'none')?'':'none';
			if (prevblock != block) {
				shb(prevblock, true);
				prevblock = block;
			};
		};
	};
};
function clb() {
	var i = 1, b;
	while((b = document.getElementById('b'+(i++))) != null) b.style.display = 'none';
};