cant install fastcgi ubuntu server: Package libapache2-mod-fastcgi is not available

libapache2-mod-fastcgi can be found in multiverse. If I remember correctly, a default installation of Ubuntu used not to enable multiverse (but should nowadays).

Maybe its disabled on your system and you'll have to add it to the list of repositories (as easy as editing /etc/apt/sources.list and appending multiverse after main or using the graphical packet manager).

Debian ships libapache2-mod-fastcgi as part of non-free by the way, so that's probably a licence issue.