I answered this question on another thread, but I'll repeat it here for others.
Yes, Knowledge Base Article #6179 wants you to set the Field options on a local machine under FileMaker Pro, because you can't do this from Instant Web Publishing.
Yes, "Define -> Database" was the option used for FileMaker Pro 8, and it has been replaced with "Manage -> Database" in versions 9 and 10.
After checking the option "Prohibit modification of value during auto entry", you can click OK to get out of Field options. You should not be in "Save Layout".
Once you go to Instant Web Publishing and enter the UNIT ID field and press tab, nothing will happen until you press Submit. Then, the lookups will execute, and you will see your values in the lookup fields.