function show_div(div_id) {
    // hide all the divs
    document.getElementById('tab1').style.display = 'none';
    document.getElementById('tab2').style.display = 'none';
    document.getElementById('tab3').style.display = 'none';
	document.getElementById('tab1tab1').className = '';
	document.getElementById('tab2tab2').className = '';
	document.getElementById('tab3tab3').className = '';

    // show the requested div
    document.getElementById(div_id).style.display = ''; <!-- add 'none' for pop-up window functionality -->
	document.getElementById(div_id+div_id).className = 'tabberactive';
	
	
}