Mac OS X: extended file attributes

When run

 ls -la 

on Mac OS X, there are some files come with @ after the file permissions:

drwxrwxrwx@ 10 user  staff    120 Sep 30 21:11 images

The @ indicates that the file has extended attributes, to see what extended attributes on the file, you can use xattr. See xattr man page.
you can delete the extended attribute using

xattr -d attr_name file