You have it set at the default, which gives read/write access to you, and only read access to everyone else. If you use
sudo chmod 777 $username /your/shared/directory
Then you'll grant full read and write access to that user. They'll need write access to upload these files from a browser--judging by the way you described the problem. Doing this will greatly reduce the security of those files, but improve the functionality. Read up a bit on permissions to find a combination that'll work for you.