var openImg = new Image();
openImg.src = "images/folderopen.gif";
var closedImg = new Image();
closedImg.src = "images/folderclosed.gif";

function showBranch(branch) 
{
    alert(branch);
    var el = document.getElementById(branch);
    toggle(el);
    swapFolder('I' + branch);
}

function swapFolder(img) 
{
    objImg = document.getElementById(img);

    if (null != objImg) {
        if (objImg.src.indexOf('images/folderclosed.gif') > -1)
            objImg.src = openImg.src;
        else
            objImg.src = closedImg.src;
    }
}

function toggle(el) 
{
    if (isShowing(el)) 
    {
        el.style.display = "none";        
    }
    else 
    {
        el.style.display = "";
    }
    
}

function isShowing(el) 
{
    return "none" != el.style.display;
}