Ben,

For all pages, which contain a data region, when you navigate away from the page, the LabKey server will notice that you have navigated away and will attempt to cancel the running database request. For small database requests, the request may be canceled instantaneously. However for larger or long running requests, the cancellation may take longer to complete.

When you navigate away from the page and the server cancels the running request, you will see a log entry in the labkey.log similar to

ERROR Table 2010-12-22 23:22:50,553 t: http-8443-Processor50 : internalExecuteQuery
org.postgresql.util.PSQLException: ERROR: canceling statement due to user request
...


For pages which do not contain a data region, if you navigate away from the page, the LabKey server has no way of knowing that you have navigated away from the page. Thus the server will not cancel the database request and it will run to completion.

I hope this answers your question.

-Brian