The Certification Matrices published by 4D, Inc. refer to platforms being "Certified" or "Compatible". What does this mean? According to the 4D 2004.6 Certification Matrix:

Certified: All product functionalities have been through validation tests. Compatible: Some tests under this environment have not been carried out. If a problem occurs, an upgrade to a 'Certified' platform is recommended.

(You can download the Certification Matrix from this page).

What this means for a 4D Developer is that if you run into a problem on a Compatible platform you should test on a Certified platform. If the problem is platform specific, it is unlikely that the problem will be addressed for a Compatible platform. Instead you should upgrade to the Certified platform.

Another implication here is that Compatible platforms will not be supported indefinitely. When a platform is marked Compatible it would be prudent to consider moving to a Certified platform so that you do not end up using an eventually unsupported platform.