I have a site have some backlink. I read somewhere that if link by site with high PR then it's consider quality link. My question is, if my site link by a page with low PR but the page is with high PR domain. Example: www.aaa.com have PR7 but www.aaa.com/page1.html have 0PR link to my site. Will this consider low quality backlink? Thanks
PR is a function of the the URLs (NOT the domains) that link to you. So if the home page of a domain is a PR8 and your URL is linked to from a page on that domain with PR0, You got some fraction of that PR0 passed to your URL. You did NOT get some fraction of the PR8 page. A VERY simplified way of looking at it is... If the page at URL XYZ is linking to your URL, URL XYZ has 100 PR "points", and there are 10 outbound links on that URL XYZ then your URL will be passed approximate 100/10 or 10 PR points. If URL XYZ has 100 PR "points" and there are 50 outbound links then URL XYZ will pass out approximately 2 PR points on each outbound links. I say approximately because there is a damping factor in the PR calculation that causes the page's PR to decay or diminish with each link. So the page will actually split 85-90% of its PR over the various outbound links. If you want to read more I'd suggest reading The Anatomy of a Large-Scale HyperTextual Web Search Engine written by Sergey Brin and Larry Page (cofounders of Google) while at Stanford. Pay special attention to section 2.1. If you still want to learn more then read their patents on PageRank.