if(document.getElementById) { 
function show_link1sub() {
document.getElementById("link1sub").style.visibility="visible";
}
function hide_link1sub() {
document.getElementById("link1sub").style.visibility="hidden";
}
function show_link2sub() {
document.getElementById("link2sub").style.visibility="visible";
}
function hide_link2sub() {
document.getElementById("link2sub").style.visibility="hidden";
}
function show_link3sub() {
document.getElementById("link3sub").style.visibility="visible";
}
function hide_link3sub() {
document.getElementById("link3sub").style.visibility="hidden";
}
function show_link4sub() {
document.getElementById("link4sub").style.visibility="visible";
}
function hide_link4sub() {
document.getElementById("link4sub").style.visibility="hidden";
}
}