function showViewer(id)
{
    prev = document.getElementById(id + '_div_prev');
    hide = document.getElementById(id + '_div_hide');
    div = document.getElementById(id + '_div');

    if (div.style.visibility == 'visible')
    {
        hideViewer(id);
        return;
    }
        
    
    prev.style.visibility = 'hidden';
    div.style.visibility = 'visible';
    hide.style.visibility = 'visible';
    
    div.style.display = 'block';
    prev.style.display = 'none';
    hide.style.display = 'inline';
}

function hideViewer(id)
{
    prev = document.getElementById(id + '_div_prev');
    hide = document.getElementById(id + '_div_hide');
    div = document.getElementById(id + '_div');

    div.style.visibility = 'hidden';
    prev.style.visibility = 'visible';
    hide.style.visibility = 'hidden';
    
    prev.style.display = 'inline';
    div.style.display = 'none';
    hide.style.display = 'none';
}