I have a link on a page:

<img id="po_Menu" src="images/menu_plus.jpg"> <a href="po()">show/hide</a>

that causes a <div id="po" style="display:none;">some html</div> to show or hide.

function po(){
    po = document.getElementById('po').style.display;
    if (po == "none"){
        document.getElementById('po').style.display = 'block';
        document.getElementById('po_Menu').src = "images/menu_dash.jpg";
    }
    else
    {
        document.getElementById('po').style.display = 'none';
        document.getElementById('po_Menu').src = "images/menu_plus.jpg";        
    }
}

The first time the hide/show link is clicked, the <div> is displayed. Any time after that, the link does nothing and I don’t see why. I did try conversely setting the <div style="display:block;"> and clicking the link caused the <div> to hide. Subsequently, the <div> would not show. I am not seeing why this does not work. I have the exact same thing elsewhere on the page and that <div> toggles.