I will probably get a bashing for saying this, but I think so yes, quality content does affect your pagerank.

Google uses Flesch-Kincaid and other custom built technology to test content so the better the grammer and spelling the less chance you will have of your pagerank being devalued.

Sites with poor and overlapped content will have their pagerank lowered which affects ranking in organic serps. Bearing in mind, you only need 20 or so crappy links for a PR1 and around 60 decent links for PR3 and 100 for PR4. This is all variable, just one PR5 link could give you a PR of 4, so just focus on quality relevant links and good content.

I always thought PR was update every 3-5 months but are you saying they changed it twice in one week?

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Pageranks updated some days ago after about 3 months.
Pagerank has mathematical formula and in this formula, quality content doesn't have any effect and only dofollow and high pagerank backlinks have effect on it. It also doesn't relate to number of backlinks. For example one pagerank 10 dofollow backlink, can increase your pagerank to 7 or 8.

my site got pr1 in 40 days, but internal post links are still 0. i checked with Internal PR Pagerank Checker

I'm surprised by this as well! I got my website up 2 PR points and my youtube videos from PR0 to PR6! I guess commenting on high PR youtube accounts works.

Recent Google PR Update badly hits my site mcqQuestions.com
That site has previously PR1 and few days ago that shows PR0 but today while checking OMG...! that shows N/A I one of my friend told me that that is the effect of Google Panda or Google Penguin...!

I think google pr always being updated weekly,and quality content always play a key role.

It's continue job. Google page rank keeps updating every-time. however major updation of page rank done once in 4 months.

Recently I noticed page rank, one of my sites, has pr 2 (home page) and its inner pages have pr2, which were pr0.

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