<div class="changeable">
<div id="block-1" class="block visible">Первый</div>
<div id="block-2" class="block">Второй</div>
</div>div.block {
display: none;
}
div.block.visible {
display: block;
}$('.block').on('click', function(){
$(this).closest('.changeable').find('.block').toggleClass('visible');
});