Unable to edit any file in /var/www
 

I can't create or edit or delete any file in /var/www, it is owned by www-data:
ls -ld /var/www/
drwxrwxr-x 4 www-data www-data 4096 2008-01-28 21:06 /var/www/

I added my username to the group www-data:
groups user1
user1 : user1 adm dialout cdrom floppy audio dip www-data video plugdev scanner netdev lpadmin powerdev admin

The directory /var/www/ has permissions 775, what is wrong? why I can't write?

Thank you

Perhaps it is a different partition and you are trying to write to a R(ead) O(nly).

Check inside the directory whether umask is making impossible your task...

In a third, last and non probable approach you could see whether exchanging to another user allow you a normal access so the problem could be caused by the user definition in whatever weird setup context you could note lately.