var subs_array = new Array("sub1","sub2","sub3");// Put the id's of your hidden divs in this array

function displaySubs(the_sub){
if (document.getElementById(the_sub).style.display==""){
document.getElementById(the_sub).style.display = "none";return
}
for (i=0;i<subs_array.length;i++){
var my_sub = document.getElementById(subs_array[i]);
my_sub.style.display = "none";
}
document.getElementById(the_sub).style.display = "";
}