That’s true !
Let’s go through this.
If you are navigating by id, and there is a chance that the next sequential id has been deleted, then the idea of incrementing by +/- 1 will not be reliable.
In this case you could add two separate recordsets to the page – I can’t think of another way of doing it
The first recordset will determine the id of the record higher than the current one
The second recordset will determine the id of the record lower than the current one
In the case of moving from the last record to the first, and back again, you also need a recordset, showing the minimum id and maximum id of the artwork table, and use some logic to determine the link id
<a href="artwork-details.php?id=<?php echo $totalRows_rspreviousid == 0 ? $row_rsminmaxid['MaxID']:(isset($_GET['id'])?$row_rspreviousid['id']:1);?>">
the link for the previous record looks like above.
the pseudologic is, if there is no lower id, go to the max id, otherwise go to the previous id, if there is a get parameter.
rather than explain how to do the recordsets, i added them to the page you supplied.
please look through the code and try to work out how it works -