[moskitos80]

Ну, без jQ вот как вариант:

function addClass (element, className) {
    if (hasClass(element, className)) {
        return;
    }
    element.className = element.className.length > 0 ?
        element.className + " " + className : 
        className;
}
function removeClass (element, className) {
    var pattern = new RegExp("\\s?" + className);
    element.className = element.className.replace(pattern, "");
}
function hasClass(element, className) {
    return element.className.indexOf(className) !== -1;
}

function toggleInherited(linkObj, expand) {
    var base = linkObj.id,
        list = document.getElementById(base + "-list"),
        summary = document.getElementById(base + "-summary"),
        trigger = document.getElementById(base + "-trigger"),
        doHasClassClosed = hasClass(linkObj, "closed"),
        doHasClassOpened = hasClass(linkObj, "opened");
    
    if ( (expand == null && doHasClassClosed) || expand ) {
        list.style.display = "none";
        summary.style.display = "block";
        trigger.src = toRoot + "assets/images/triangle-opened.png";
        removeClass(linkObj, "closed");
        addClass(linkObj, "opened");
    } else if ( (expand == null && doHasClassOpened) || (expand == false) ) {
        list.style.display = "block";
        summary.style.display = "none";
        trigger.src = toRoot + "assets/images/triangle-closed.png";        
        removeClass(linkObj, "opened");
        addClass(linkObj, "closed");
    }
    return false;
}