When Apache under OS X throws 'Forbidden' errors on files under the ~/Sites path, and the error log report 'Permission denied: access to /somefile/blah failed because search permissions are missing on a component of the path', check a missing Other Execute permission along the entire path.

"If you want someone to have access to a file in a particular folder, that user must have "search" permission (the "x") on all of the folders along the path from the top of the drive down to the folder where the file is. And then the file itself must have "read" permission for that user. And if you want someone to be able to see what files are in a particular folder, that folder must have "read" permission for that user."