I'm a Web Designer and when I open some PSD files in my Photoshop CS3 (Windows 7) I get these messages pop-up before to open PSD. My fellow designer use Photoshop on Mac OSX.
Error 1
Some text layers contain fonts that are missing. These layers will need to have the missing fonts replaced before they can be used for vector based output.
Error 2
Some groups were found corrupted and repaired.
Error 3
This document contains unknown data which will be discarded to keep layers editable. To preserve the origional appearance instead, choose Flatten to load composite data as a flattened image.