hideOrShow = function(tagId)
{
    var tag = document.getElementById(tagId);
    //obj.classSave is the attribute to hold the normal css-class.
    //when a hidden folder is going to be expanded,this css-class could be used.
    if(tag!=null)
    {
	    if(tag.style.display=="")
	    {
		    tag.style.display = "none";
	    }
	    else
	    {
		    tag.style.display = "";
	    }
    }
    else
    {
	    error("the controller or the folder has not been assigned!");
    }
}