Some people, including me, have put web pages in their personal Sites folder (~/Sites), then turned on Web Sharing and tried to display those web pages. Instead of seeing our web pages, we see
"403 Forbidden. You don't have permission to access"
I found an explanation of how to fix the problem in
I followed that web pages "Activate All User Accounts" instructions, and created a file called /private/etc/apache2/users/local.conf. Now I can see my web pages - both on the computer that contains the web pages, and also on another computer which is connected to the Internet.
The only changes that I'd put into the gigoblog explanation are these:
1) Make sure that you're signed on as a system administrator before you start typing commands in Terminal.
2) After you're done, if you don't usually log onto your Mac as an adminstrator, exit from your administrator session.