The goal of this phase is to produce a site that is live and 90%-100% "feature complete" and allows you to begin to publish your content.  Secondarily we may also identify any minor issues that may remain unresolved in the deisgn phase and make some adjustments.

This entails the actual programming of back-end support for populating and dynamically laying out the various entities and organizational structures identified in the Information Design Phase.   For example, you can now actually add a new Event to the site's “Upcoming Events” page by creating a "Event Item" object in the Content Management System.  You can fill out the fields of the Event, click "save and publish" and it will appear nicely laid-out on the actual site.
 
In general "feature complete" means that intended features work reasonably well but are not necessarily in 100% finalized form.
This phase can roughly take between 1-6 weeks, but this various widely with the complexity of the site.