From Facebook Developer Wiki

Facebook will deprecate profile boxes in late 2009/early 2010.

To integrate into the profile, use application tabs. For more information, please read the Developer Roadmap.

[edit] Narrow Profile Boxes on the Main Profile

The narrow profile boxes on the main profile (Wall and Info tabs) have the same width as narrow profile boxes (200 pixels, with 8 pixels of padding on each side for an actual usable width of 184 pixels) but are limited in height to 250 pixels. You create a narrow profile box for the main profile using the new profile.setFBML API profile_main parameter.

[edit] Adding a New Box to the Main Profile

A new application box can be added to the main profile when a user is on an application canvas page and clicks the Add to Profile button that the application has added to their page via the fb:add-section-button FBML tag. The Add to Profile button will only appear if the application has already called profile.setFBML with the profile_main parameter set. We recommend you call profile.setFBML after the user has entered enough data for your application to be able to make a compelling profile box.

If the user already has a box from the application, either on the main profile or in their "Boxes" tab, the Add to Profile button will not appear on that application's canvas page.

[edit] Migrating Existing Profile Boxes

When users switch to the new profile design, up to five of their existing profile boxes will be migrated to the main part of the profile, with additional boxes appearing in their "Boxes" tab. In order for a box to be migrated to the main profile at the time of launch, your application must already specify a profile box with the new profile.setFBML profile_main parameter. The profile boxes will be migrated in a top-down fashion.

Note: If you do not create new boxes that can appear on the main profile, then your existing profile boxes (specified by fb:wide and fb:narrow) will appear on the ”Boxes” tab.