Your friend >>
http://ubuntuforums.org/
Try this...
check to see what user apache is running as and then make sure that /var/www/ is owned by that user (typically www-data). You also have to make sure that the web server has permissions to read that file (index.html).
However, you can start by making an .htaccess file with this in it and place it in /var/www/.
Code:
DirectoryIndex index.html index.htm index.php
Oh... and I think apache2 gets installed by default unless I am mistaken... same with mysql.