Why are some files in ls -l on Mac OSX (Snow Leopard) tagged with "@"? [duplicate]

"They are extended attributes. ls -l@ shows them (mostly they are flags to indicate that the file is coming from the internet, in those cases, when opening the file (or installing a DMG) MacOS will ask if you really want to open it). The xattr command allows you to change them.

There is another one too. ls -lO (upper case O) shows the flags set via chflags command. ls -lO@ shows the file in it's full glory."