var opened_nav_el = null;


function navElementChange( el ){

    // if we click again on opened element don't do anything
    if ( opened_nav_el == el )
        return

    // close old opened element
    if ( opened_nav_el != null ){
        opened_nav_el.className = opened_nav_el.orgClassName;
    }

    // save currently opened element
    opened_nav_el = el;

    // change parent style
    el.orgClassName = el.className;
    el.className    = "show_childs";
}