I was configuring an apache2 setup to work with suPHP and ran into various Internal Server Error 500s due to folders and files having too generous permissions on them. suPHP doesn’t like that.
These two commands, when run from the directory where the web files reside, will recursively reset the permissions as required.
Find files and set to permissions 644
sudo find . -type f -exec chmod 644 {} \;
Find folders and set to permissions 755
sudo find . -type d -exec chmod 755 {} \;