You can encrypt access 2003 databases, though IIRC only with (at best) RC4 encryption. Since that is very easy to screw up you are somewhat dependant on MS having implemented it well.

Securing data-access pages: This applies to data that is accessed via a Web page. The Web pages are stored in the file system, so only file system security applies.

Microsoft Access 2010 Reference Guide The 2010 version of Access offers an improved format for Web-ready databases, conditionally based macros, customized database themes and conditional formatting ...