То есть как то так?
<SCRIPT LANGUAGE="JavaScript">
function getCookie(name) {
var cookie = " " + document.cookie;
var search = " " + name + "=";
var setStr = null;
var offset = 0;
var end = 0;
if (cookie.length > 0) {
offset = cookie.indexOf(search);
if (offset != -1) {
offset += search.length;
end = cookie.indexOf(";", offset)
if (end == -1) {
end = cookie.length; }
setStr = unescape(cookie.substring(offset, end)); } }
return(setStr);}
var block = document.cookie.indexOf('block');
if ( block != -1 )
{ document.getElementById('mylink').style.display = 'inline';}
else
{ document.getElementById('mylink').style.display = 'none'; }
</SCRIPT>
<span style="id='mylink'"><a href="http://test.com">Невидимая ссылка</A></span>