I've run into a rash of tar.gz files on the internet today that are not actually gzipped. People seem to be just tarring things and then renaming them tar.gz! This of course makes it difficult to ...

These steps should always work with zip files, and it also appears to work with tar.gz files. If you want to extract .rar files, though, you’ll still need to use a third-party app like iZip.

Several users have reported a problem where Firefox 1.5 has problems properly recognizing that files with the .dmg.gz extension (disk images that have been compressed using gzip).