ns4 = (document.layers) ? true:false 
ie4 = (document.all) ? true:false
ng5 = (document.getElementById) ? true:false 

function hideSec() {

if (ng5) document.getElementById('sec1').style.visibility = "hidden"
else if (ns4) document.sec1.visibility = "hide"
else if (ie4) sec1.style.visibility ="hidden"

if (ng5) document.getElementById('sec2').style.visibility = "hidden"
else if (ns4) document.sec2.visibility = "hide"
else if (ie4) sec2.style.visibility ="hidden"

if (ng5) document.getElementById('sec3').style.visibility = "hidden"
else if (ns4) document.sec3.visibility = "hide"
else if (ie4) sec3.style.visibility ="hidden"

if (ng5) document.getElementById('sec4').style.visibility = "hidden"
else if (ns4) document.sec4.visibility = "hide"
else if (ie4) sec4.style.visibility ="hidden"

}

function showSec(n) {
hideSec();
if (ng5) document.getElementById('sec' + n).style.visibility = "visible";
else if (ns4) document.layers["sec" + n].visibility = "show";
else if (ie4) document.all["sec" + n].style.visibility = "visible";
}