http://www.joomla.it/articoli-della-community/4009-inserire-una-pagina-intro-qsplash-pageq-in-joomla-15.html
OR
Sometimes we want put a index.html file with a flash intro or other stuff with a link to the joomla index.php.
But we have a little problem in Joomla with the default base URL or "Home" option because Joomla convert http://[ourhost]/index.php into http://[ourhost] and the webserver retrieve us index.html again.
The solutions is change the file modules/mod_mainmenu/helper.php
Change the next line:
$tmp->url = JURI::base();
for this
$tmp->url = 'index.php';
And now the "Home" option come back to index.php and not index.html
Then go to apache2 conf file:
C:\Program Files\Apache Software Foundation\Apache2.2\conf
Name of the file: httpd.conf
Find DirectoryIndex and make sure index.html is placed before index.php as shown below:
<IfModule dir_module>
DirectoryIndex index.html index.php
</IfModule>