function toggle(branch){
    var objBranch = document.getElementById(branch).style;
    if(objBranch.display=="block")
        objBranch.display="none";
    else
        objBranch.display="block";
}

var minusImg = new Image();
minusImg.src = "images/minus.gif";

var plusImg = new Image();
plusImg.src = "images/plus.gif";

function swapImg(img){
    objImg = document.getElementById(img);
    if(objImg.src == plusImg.src)
        objImg.src = minusImg.src;
    else
        objImg.src = plusImg.src;
}