Александр Таратин

var clickElem = document.getElementById('click');
clickElem.addEventListener('click',function(e){
    document.getElementById('main').style.display = 'block';
    clickElem.style.display = 'none';
})

$('.tree-content').hide();
$('.tree-block').hover(function () {
    $(this).children('.tree-content').show();
},

function () {
    $(this).children('.tree-content').hide();
});