Can't use LAMP in ubuntu 11.10

[billaboy]

I've installed LAMP in my ubuntu 11.10...

Also, have installed phpMyAdmin...
phpMyAdmin is working properly...

But when I try to access "localhost" it shows error...

.php pages error comes is
"Server error
The website encountered an error while retrieving http://localhost/. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later."



.html pages show error stating
"Forbidden

You don't have permission to access /index.html on this server.

Apache/2.2.20 (Ubuntu) Server at localhost Port 80"


What should I do..??
Also, why don't both the type of files show same error...??

Help.......!!!!!!

Regards,
Billaboy