[Usability] How to limit the MB of the Trash folder

[Tim McConnell <tmick1 earthlink net>]

Hi, 
I would like to put a quota or limit  on the .Trash file and make it display a message if the size approaches the limit. Is this possible?

The reason for this is I received this Error: 
GDM could not write to the authorization file. This could mean you are out of disk space or that your home directory could not be opened for writing. In any case it is not possible to log in. 
Please contact your system administrator. 
It turns out that the trash was full and so was my user's /home directory. 

I would love to prevent this from EVER happening again! 
Thanks in advance, any suggestions welcome.