function bookm_switch(elem) {
	if (elem == 'bookmark_1') {
		a = 'bookmark_1';
		b = 'bookmark_2';
	}
	if (elem == 'bookmark_2') {
		b = 'bookmark_1';
		a = 'bookmark_2';
	}
	document.getElementById(b).className = 'unactive';
	document.getElementById(a).className = 'active';
	document.getElementById(b + '_div').style.display = 'none';
	document.getElementById(a + '_div').style.display = 'block';
}