doba=5000
pocet = 5
rotator=1

function rotate() {

document.getElementById('top1').className='block-off';
document.getElementById('top-li1').className='';

document.getElementById('top2').className='block-off';
document.getElementById('top-li2').className='';

document.getElementById('top3').className='block-off';
document.getElementById('top-li3').className='';

document.getElementById('top4').className='block-off';
document.getElementById('top-li4').className='';

document.getElementById('top5').className='block-off';
document.getElementById('top-li5').className='';

document.getElementById('top'+rotator+'').className='block-on';
document.getElementById('top-li'+rotator+'').className='active';
rotator = rotator + 1
if (rotator>pocet) {rotator=1;}
}

window.setInterval("rotate();",5000)