updating IDs after delete  is considered a very bad practice. i suggest u not to do that. there are ways like:
lock the table, fetch the whole table, write the records  again with new IDs.
but u have to free ur design from this.
a better way is to have a code field  and work with that.
if u delete a recorde u may find the deleted code and reuse it.this has nothing to do with the ID.
Have More Fun.