What's the "@"mark at the file description? I installed princexml for Mac. With ls -alF, I have -rwxr-xr-x@ 1 prosseek  admin  14190120 Jun  8 16:11 prince*. What's the meaning of @ in -rwxr-xr-x@?

And when I tried to execute the binary, I got ./prince: Operation not permitted error message. Does this have anything with @?
It means that the file has extended attributes. To see these attributes, run xattr -l file, to see the extended attributes of a particular file, or ls -l@ to see the extended attributes of all files in a particular directory.

See the man page for xattr as well.