function showhide(layer_ref)
{
    if (document.getElementById) 
    {
       hza = document.getElementById(layer_ref);
       var state = hza.style.display;

        if(state == 'block')
        {
           state = 'none';
        }else
        {
            state = 'block';
        }
        
        hza.style.display = state;
    }
}