Web databases take some planning
As a final step in the design process, decide whether you'll publish your database to SharePoint. If you will, then your tables can't use some of the features that Access provides. For example, you can only use Datasheet view to create tables, not the table designer. In addition, the only types of relationships you can create are called Lookup Fields. That's a type of relationship that allows you to select the values that reside in one table from a list in another table.
Access imposes those limits because the publishing process converts your database to Dynamic HTML and ECMAScript, so you need to avoid creating any database components – Access calls them objects – that can't be converted into those languages.
So, as a final step in your plan, note whether you'll publish the database. It's a small detail, but it's critical. The Quick Reference Card has links to information about creating databases for use with SharePoint.