I am looking for specific software but can't tell if anything is offered is for Macintosh. I just need to know how I can identify Mac files before I download them. Can this be done? How can you tell? If not, is there much available for Mac?

After downloading the program I need for an hour, it showed up as a Simple Text file that could not be opened by Simple Text or anything else as far as I know. It was not supposed to be a Simple Text file. Could this be a PC file?

Thanks for your help!
Paintera