function show_hide(id)
{
var id = document.getElementById(id) ;
    if (id.style.display == "none")
    {
        id.style.display = "block";
    }
    else 
    {
        id.style.display = "none";
    }
}

function arrow_change(img)
{
var img = document.getElementById(img) ;
	
    if (img.style.backgroundImage == "url(images/arrow_down.gif)")
    {
        img.style.backgroundImage = "url(images/arrow_up.gif)";
    }
    else 
    {
        img.style.backgroundImage = "url(images/arrow_down.gif)";
    }
}