DocumentRoot  "/Library/WebServer/Documents"
<Directory "/Library/WebServer/Documents">

DocumentRoot "/Users/bob/Sites"
<Directory "/Users/bob/Sites">

<VirtualHost *:80>
    DocumentRoot "/Users/username/Sites"
    ServerName localhost
</VirtualHost>

<Directory "/Users/username/Sites/">
    Options Indexes MultiViews
    AllowOverride All
    Order allow,deny
    Allow from all
</Directory>