Thanks for your reply, let me try to describe my scenario in more detail.
When we have a new user, I will create the user in AD and then sync it to
the SharePoint profiles.
So, when the user is required to be removed. I delete the user in AD, then
sync it to SharePoint profiles.
Then, I go to Document Library and see the files uploaded by that user. User
name still appears next the file. Then I click the user name, the user
profile still appear. But there is a button called "Delete this user from
site collection".
So, I click that button to delete the user from site collection. After that,
I go back to Document Library, and click the user name. An error message
"User not found" is shown. It is good!
However, there is still a problem. If I go to a Publishing site that was
created by the user, try to open the Page Settings. The error message "User
not found" is shown. That's really a problem, because I cannot change the
Page Settings anymore as the creator user was deleted.
That's why, I was asking you, what're the correct steps to delete a user.
Did I make anything wrong?