function mouseover(obj) {
    if(obj.className == 'focus') return ;
    var targetTag = obj.id == 'catalogNav' ? 'historyNav' : 'catalogNav';
    document.getElementById(targetTag).className = 'blur';
    obj.className = 'focus';
    if(targetTag == 'catalogNav') {
        document.getElementById('historyList').style.display = 'block';
        document.getElementById('catalogList').style.display = 'none';
        document.getElementById('recycle').style.display = 'block';
    }
    else {
        document.getElementById('catalogList').style.display = 'block';
        document.getElementById('historyList').style.display = 'none';
        document.getElementById('recycle').style.display = 'none';
    }
}