I have running multilanguage site, but right now not all pages are translated. Right now it working particulary good - untranslated pages just show text of a default language. I would like to add some automatic generated text at top of these pages like "we are sorry this page is only available in english language" (and under that text in original text in czech language).

Also I have default language czech, second english and I would like to add third language german. In this case when I switch to german language and dont have translated some specific page in german lang. it will be display czech translation. I think in this case it would be better to display english translation instead (since a lot of german people know english, but only a few know czech).

Could someone please help me with these issues? I know few thing about php and so, but really dont know where to start with this..