PR Question..

Websites don't "have page ranks", Gerald. Only pages have page ranks. What you're referring to as a "PR5 website" is actually a website whose own home page happens to be PR5. If your backlink is on its own home page, that means something. But even then, what it means is of course divided between the number of links on that page and is therefore in inverse proportion to their number.

And actually, this is the place to discuss it, anyway: Adsense / PPC / SEO Discussion Forum

If the pr3 health website doesn't link to any other sites (or links to only a few ones) some PR/link juice will be distributed to the cancer site but it won't matter as much in terms of boosting it's rankings as it would if the PR5 computer website would have been health related. The reason behind this is that nowadays you can grow a pr 4-5 website by inflating it with tons of non-relative links. Simply having a PR 5 site doesn't mean it will rank as you would expect unless it is a PR5 site that got there by bringing only relative links to it.

A PR 3-4 website that got there with only relative links will rank much better than a PR 5 site that only has general links to it. For example if you buy a pr4-5 domain from Godaddy auctions, and you choose to make it a site that has nothing to do with the old website on that domain, the pr will remain but there will be no good rankings. Instead, if you keep the niche/field that the old site used to rank for, it will rank very well. This is just from my tests from the past years, not a general rule of thumb.

Actually what you are talking about has been not valid in terms google rules . So If you do such thing all three sites of your will be penalize or you pr will be decrease gradually . So request to built organic links from authorized sites like .edu or .gov or health regarding bolgs which will increase your traffic of your page . you can also take help of social media.

If you link from the PR3 to your Health website as it is relevant. Yes it will get good Google Juice. Simple.

Relevancy, Low outbound link, Quality content on an actual PR page is what you need.

Ofcourse, you link to high PR page with quite a huge number of outbound links and not related to your niche, you will still rank but it's nothing as strong as a stand alone site. You also risk penalty someday.

The site that are linked from the relevant site (health) can get some good PR juice and doesn't matter from where those sites (health) further linked from.