Localhost apache2 webserver WAS running ok on Ubuntu 13.04.
I changed permission on /var/www/ so that I could access it with my non root account. It's a standalone server used only by myself for testing.
Now localhost does not run at all
Ping localhost shows server IS running.

The browser error is:

Unable to connect
Firefox can't establish a connection to the server at localhost.

What should I be checking to resolve this?

With thanks.