function _collapseExpand(collapsedDiv, collapsedImg, imagePath)
{
    var content = document.getElementById(collapsedDiv);
    var image = document.getElementById(collapsedImg);

 /* 隱藏，但是仍然在網頁上佔據空間：
    if (content.style.visibility == 'hidden')
    {   content.style.visibility = 'visible';
        image.src = imagePath + '/minus.gif';  }
    else {   content.style.visibility = 'hidden';
             image.src = imagePath + '/plus.gif';  } */

 /* 隱藏，而且在網頁上收合：*/
    if (content.style.display == 'none')
    {   content.style.display = 'block';
        image.src = imagePath + '/minus.gif';  }
    else {   content.style.display = 'none';
             image.src = imagePath + '/plus.gif';  }   
}