<Directory "/Users/{username}/Sites">
Options Indexes MultiViews
AllowOverride All
Order allow,deny
Allow from all
</Directory>
4 chmod 755 ./{username}.conf
5 sudo mkdir ~/Sites
6 browser
http://localhost/~{username}
Then it works . But do not forget the character '~'
'~/Sites' directory will be the user level tomcat server directory , while '/Library/WebServer/Documents' is the directory of system level.
There is a good Reference here : Install and configure Apache, MySQL, PHP and phpMyAdmin on OSX 10.8 Mountain Lion