The easiest way would be using ODBC and the MS Access ODBC driver - this is probably free to use on licenced windows servers.
Failing that, you'd probably have to buy an expensive third party ODBC driver which might be available on non-win32 systems too.
I don't recommend using MSAccess for a web back-end in any circumstances - the driver is liable to problems like crashing, hanging etc. It would probably be better to write some sort of converter which loads it into another DB and access it from there.
Mark