deleted files don't go to the trash

It is possible you have copied some files from another computer and they don't have the right permissions or Access Control Lists (ACL). Try "Get Info" on a file and look at "Sharing and Permissions".

Alternatively, you can use "ls -le" from a terminal window. Normally files and directories will belong to your username and have group "staff". The third flag bit should be "w" to give the username (you) permission to write to the file or directory.

-rwxr-xr-x 1 username staff 537 Oct 1 2012 hello

drwxr-xr-x 3 username staff 102 Feb 28 22:34 world

That would explain the dialog. I am not sure why the files don't end up in the Trash, but that might be a permission problem as well.

Eagle Owl, Queenslander is saying "Lately whenever I delete any files by moving them to the trash, the following window appears:"; if it applies to any files it is more likely that it is a permissions problem or access control list problem with the Trash itself than with the files moved to the Trash.

Queenslander, check the permissions on your Trash folder:

In the Terminal type:

ls -adle ~/.Trash

You should see drwx------ permissions.

Good! 🙂

That's awesome your problem was fixed. 🙂

<Edited By Host>

How did you go about changing the Read Write permissions on your enclosed folder? Just with Get Info? I tried this, and permissions seem to be what Eagle Owl has listed, but I still cannot see files in trash. They must be hiding someplace... because the available space on my hard drive does not increase after I select 'OK' from the "Finder wants to make changes..." dialogue you showed in the first screenshot... thanks!

Hey Catherine, hopefully you were able to fix your issue! In the future, especially with closed issues such as this one, I'd reccomend creating a new thread for your issue as you'll get a more prompt response and attention to your issue specifically!
For both Catherine and those coming through Google, you can change the permissions by copying/pasting the following commands into terminal (go -> utilities -> terminal).
mkdir ~/.Trash

If your system informs you that the "file exists", you can ignore in and move on.
Next copy and paste the following line, followed by the Return key:

sudo chown $UID ~/.Trash

This time Terminal will ask for your Admin password -the one you log into your mac with. As an FYI, this won't appear as if anything is typing, I promise, it is. It's going to be black text on a black background for security reasons, but you won't see the asterisks you're used to. Type slow, and hit return.

Next copy and paste the following:

chmod u+rwx ~/.Trash

Essentially what we're doing with these commands are:
1) Making sure that the ~/.Trash directory even exists
2) Changing the "owner" of that directory
3) Setting permission level for it.

It should end up looking like this:

Last login: Tue Apr 08 05:00:53 on ttys000

YourComputerNameHere:~ yourusername$ mkdir ~/.Trash

mkdir: /Users/yourusername/.Trash: File exists

YourComputerNameHere:~ yourusername$ sudo chown $UID ~/.Trash

Password: (type your password then press Return)

YourComputerNameHere:~ yourusername$ chmod u+rwx ~/.Trash

YourComputerNameHere:~ yourusername$

Your detailed direction work accurately for me. Thank you 🙂

Your directions worked perfectly. Thanks for making it so easy to copy and paste! I have one concern though: I wasn't asked for my password. Should I be worried?

Worked perfectly, thank you ! 🙂