The solution provided in this answer is yet effective for your needs even in Ubuntu 12.04.
Placed here for your convenience. 
You can change your default folder for www content by editing the
  information provided inside the /etc/apache2/sites-available/default
  file. By dropping sudo gedit /etc/apache2/sites-available/default
  and changing any occurrence of the /var/www or (maybe your case)
  /var/www/html and setting the folder that you wish to use.
The contents of the file will look like this:
<VirtualHost *:80>
  ServerAdmin webmaster@localhost
  DocumentRoot /home/geppettvs/www
  <Directory />
      Options FollowSymLinks
      AllowOverride None
  </Directory>
  <Directory /home/geppettvs/www/>
      Options Indexes FollowSymLinks MultiViews
      AllowOverride None
      Order allow,deny
      allow from all
  </Directory>
  ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
  <Directory "/usr/lib/cgi-bin">
      AllowOverride None
      Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
      Order allow,deny
      Allow from all
  </Directory>
  ErrorLog ${APACHE_LOG_DIR}/error.log
  # Possible values include: debug, info, notice, warn, error, crit,
  # alert, emerg.
  LogLevel warn
  CustomLog ${APACHE_LOG_DIR}/access.log combined
    Alias /doc/ "/usr/share/doc/"
    <Directory "/usr/share/doc/">
        Options Indexes MultiViews FollowSymLinks
        AllowOverride None
        Order deny,allow
        Deny from all
        Allow from 127.0.0.0/255.0.0.0 ::1/128
    </Directory>
</VirtualHost>
In this case I am using my /home/geppettvs/www folder in order to
  place the files that will be exposed to the public via http
  connections (port 80).
Give this a try. I hope this help you.
However, I suggest you to run a search before opening a new question. Your question may be closed as du
Good luck!