If a "?" is shown before any of the buttons above, then this indicates that the stream has been reported to be dead and is unlikely to work. It may still be worth giving it a try in case it has returned to service since the last database update.
For mp3 and AAC+ stream formats, we recommend using Winamp for Windows PC and VLC media player for Mac and Linux. AAC/AAC+ (HLS) and Ogg FLAC streams should be played using MPC-HC for Windows PC and VLC media player for Mac and Linux.