I don't the the exact reason why, but all the files in my home directory have 0620 file permission. What I remember is that I setup file sharing in System Preference.
Now, when I try to delete file in my home directory, this dialog box pops up to ask the password. I modified all the files back to permission 0774, but I still can't delete the file without answering the password.
What went wrong? How can I get the system back to normal? I use Mac OS X Lion 10.7.2.
Refer to this post also