Care has to be taken when uploading files containing special Macintosh information to make sure those files will work properly when downloaded to another Macintosh. They must be encoded in a format that will preserve the Macintosh information by putting it all in the data fork. The upload formats that preserve Macintosh information are MacBinary, BinHex, AppleSingle, StuffIt X Archive, and Zip Archive.

To create a Zip Archive using Mac OS X, either Control-click on the file or folder and choose Create Archive (which is Apple-speak for "make a compressed ZIP file"). Or you can click on a file, then go to the Action menu (the button that looks like a gear up in the Finder window's toolbar), and choose Create Archive from there. Either way, it quickly creates a new file, with the file extension ".zip". This is the compressed file. You can also compress several different files (like three, for example) into one single archive file - just Command-click (or Shift-click contiguous files) on all the files you want included, then choose Create Archive of X Items from the Action menu. A file will be created named "Archive.zip" Please be sure to change the name of your zipped file to something relevant prior to uploading.