Medar is correct. By removing the hyperlink you are not allowing anyone to see who is online. However in order to make the w3t_Online table not to be populated by any information whatsoever then you will need to make some changes to the code, mainly to ubbt.inc.php and partly to ubbthreads.php.
On the ubbt.inc.php you will need to comment out the sections where the w3t_Online table is populated while on the ubbthreads.php (and tmpl) you will need to get rid of the Max users online was.... and There are so and so registered members..
This approach will not only get rid of the Who's online pages (so even if anyone can see the page the data won't be there) but it will also reduce the queries in your database.
