function switch_tabs(tab) {
	var tabs = document.getElementById('tabs').getElementsByTagName('li').length;
	//switch off other tabs and their respective content
	for (i=0; i < tabs; i++) {
		document.getElementById('tab'+(i+1)).className ='';
		document.getElementById('tab'+(i+1)+'_content').style.display = 'none';
	}
	//switch on selected tab and its respective content
	document.getElementById(tab).className = 'moveTab';
	document.getElementById(tab+'_content').style.display = 'block';
}