What security issues do I need to worry about on my new site?

Thanks to the help of everyone in the forums, I was finally able to launch my store. I really appreciate all of your contributions and I have learned a lot on here.

Since I have never had a site before, I wanted to make sure it is safe. First of all, I am just using Paypal as a payment method so I don't think I need to worry about any customers information since that will all be handled through Paypal. Please correct me if I am wrong.

As far as when I went to edit files and changed the attributes from 644 to 777, do I need to change those back? Are those just to prevent ME from accidently changing files, or can the public mess with those if they are not changed back? Is the only way to get into things and change files with an admin logon and password?

For backups, the control panel has a complete backup wizard that backups the entire web structure and SQL database and puts it in a zip file. I have been doing that and saving them locally. I suppose I should probably do that weekly or so.

Please let me know if there is anything else I should consider. Thanks again for all your help and hopefully I can start helping people on here too someday.

In your /docs/ directory, there is a section on securing your site.