function showhide(id) {

    var ukrywany = 'div';
    var ukrywajacy = 'a';

    this.id = id;

    this.click = function () {
        el_node = this;
        do {
            el_node = el_node.nextSibling;
        } while (el_node.nodeName.toLowerCase() != ukrywany)

        el_node.style.display = el_node.style.display == 'none' ? 'block' : 'none';
        this.className = (el_node.style.display == 'none' ? 'closed' : 'opened');
        return;
    }

    this.start = function (el) {
        for (var i = 0, el_node; i < el.childNodes.length; i++) {
            el_node = el.childNodes.item(i);
            if (el_node.nodeName.toLowerCase() == ukrywajacy) {
                el_node.className = 'closed';
                el_node.style.cursor = 'pointer';
                el_node.onclick = this.click;
            }
            else if (el_node.nodeName.toLowerCase() == ukrywany) {
                el_node.style.display = 'none';
            }
        }
    }

    if (document.getElementById && document.childNodes) {
        this.start(document.getElementById(this.id));
    }

}