I have read so many articles and I still don't understand the distribution of link juice in increasing one page's page rank. Here is my question. For example DP has PR 6 and it's SEO category has PR 4 and this thread is PR 0. Does this PR 0 thread will receive some link juice? If yes which link juice will be come from? Is it from the home page of DP or it is from the category which this thread included?
DP has a PR of 6 because that is the top level page in the website. the SEO category has a PR 4 because a lot of outside sources link to the SEO category (and juice flows down). My theory is that some juice will pass the this post, but not enough to show up on the Google Tool bar. Keep in mind that that DP is a old and trusted site in the search engines eyes. This helps with the high PR. In order for your thread to get link juice it will need to generate its own inbound links. "hey this is a great thread, check it out here is a link" - this is the response you want when people read your post. Also, keep in mind that you should not put all of your trust in the google tool bar. It does not show all. hope my two cents help
Page Rank is simply a measure of link popularity - how many inbound links a page has... and how strong each of those links are. All of the major engines likely have their own version of Page Rank. Not all inbound links are created equally. In fact it would be rare for 2 inbound links to pass the same amount of PR or "juice". All pages on the web start out with a miniscule amount of PR... I mean microscopic. As the page gains followed links from other indexed pages on the site (internal inbound links) and from indexed pages on other sites (external inbound links), it gains page rank. The reason most home pages have the highest PR of all pages on the site is that 1) every page on the site typically links to the home page at least once (sometimes more) because HOME is almost always in the global navigation and 2) other sites tend to link to the home page more often than to inner pages on a site. Typically the pages linked to in the global navigation will have the second highest PR, because the home page and every other page on the site links to them. The deeper you drill into a site, typically the lower the page rank of those deep pages... UNLESS a deep page has a high number of inbound links or some high quality (strong) inbound links passing them lots of juice in which it might have a higher page rank than its parent page. You can checkout my post that should give you a decent understand of what is Google Page Rank. Page Rank gets confusing because there are actually 2 types of Page Rank... the "real" page rank of a URL and the toolbar page rank. The post should clear some of that up for you.