If you were to log in, you'd be able to get more information on your fellow community member.
JPEG or GIF. It is funny but many programmers that write their own software does not know what format to use for screenshots. I run a big site about Total Commander, and if don't make a notice to my users they upload screenshots of thier software plugins in JPEG format not in GIF. It is a big mistake. Screenshots in GIF are usually much smaller and does not lose quality!