var state = 'none'; 
function showhide(layer_ref){ 
    if(state == 'block'){ 
        state = 'none'; 
    }else{ 
        state = 'block'; 
    } 
    if(document.all){ //IS IE 4 or 5 (or 6 beta) 
        eval("document.all." +layer_ref+ ".style.display = state"); 
    } 
    if (document.layers) { //IS NETSCAPE 4 or below 
        document.layers[layer_ref].display = state; 
    } 
    if (document.getElementById &&!document.all) { 
        hza = document.getElementById(layer_ref); 
        hza.style.display = state; 
    } 
}