Active Forums is always tested for cross-browser compatibility just prior to release. However, after every release we always see an increase in requests related to layout or design issues. We aren't perfect and occasionally we do miss a few css tweaks here and there. The majority of the time the problem is within your browser. Something as simple as clearing your browser cache or holding down the ctrl key and clicking refresh will almost always clear up the problem.
There are also situations where a skin could be causing the problem and interfering with the default css in Active Forums. It is impossible for us to test on every skin available for DotNetNuke, but we will do our best to help you resolve the issue you are having.
We will also add screen shots to the Active Forums Knowledge Base that will be a reference as to how the various screens should appear when accessed with the major browsers.