/**
 * Opens or closes a html list of elements.
 *
 * @param        string        listName
 */
function openList(listName, save, openTitle, closeTitle) {
        var element = document.getElementById(listName);
        var status = 0;
        if (element.style.display == 'none') {
                // open list
                element.style.display = '';
                status = 1;
                var image = document.getElementById(listName + 'Image');
                if (image) {
                        image.src = image.src.replace(/plus/, 'minus');
                        if (closeTitle) image.title = closeTitle;
                }
        }
        else {
                // close list
                element.style.display = 'none';
                var image = document.getElementById(listName + 'Image');
                if (image) {
                        image.src = image.src.replace(/minus/, 'plus');
                        if (openTitle) image.title = openTitle;
                }
        }

        // save new status in session (use ajax)
        if (save) saveStatus(listName, status);

        return true;
}