I realized that there are sites out there which have a high PR (5 and above) but after clicking on one link which leads to one subpage the PR gets down to 0. How can someone control the PR heredity on his site?
The pages which have a lot of links will have a higher PR. For Example: http://www.dinosaurfact.net/groups.php is a zero becuase people who randomly entered the site did not find the information usful enough to link it. "talk about it on their website, forum, etc". I didn't add links for it as well. but http://www.dinosaurfact.net/dinoextinct.php is a three 3 becuase people and myself have been building links around the internet to that page.
This is most like got to do with the site link structure. Make sure that all the pages are inter connected with each other using links.
On most websites, it's only the home page that gets links from pages outside the site. The links between pages within the site can then help spread PR to the subpages on the site. If you want to have the best chance of raising the rank of a subpage, it should be linked from every other page in the site. If you have hundreds of pages this becomes impossible so only a handful of pages can get linked in this way; these pages end up with higer PR while the remainder have a lower PR, sometimes even 0.
generally spoken you are right, but: http://www.tui.com/angebote/last-minute/tuerkei-antalya.html this page has a PR of 2 and 0 backlinks. so it must be connected to the inner linking of the site like brian and lycos said. but is it really advisable to link to evey subpage from anywhere. I think this could lead to theme bleeding.