function toggleButton(tar,div)
        {
            //reset//
            document.getElementById('image1').src = '/images/sidebar/categories.png';
            document.getElementById('image2').src = '/images/sidebar/popular.png';
            
            document.getElementById('content1').style.display = 'none';
            document.getElementById('content2').style.display = 'none';
            
            //activate//
            document.getElementById(div).style.display = 'block';
            
            if(tar == 'image1')
                document.getElementById('image1').src = '/images/sidebar/categories-on.png';
            else
                document.getElementById('image2').src = '/images/sidebar/popular-on.png';
        }