This month, i saw the pagerank of a number of my sites being improved, and it means that google has updated its pagerank for this month. Is anyone else has noticed it or is it just me or is updating pagerank is not a whole affair from google and they update it on an individual sites basis?

REAL PR is updated continuously for every page

the Toolbar PR is only updated occasionally

PR is NOT assigned to individual sites it is assigned to individual pages.

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Update of PR on the Google toolbar is usually done every three months.

Have not seen any notable increase in our site's PR for the first quarter though. Might have to wait for the comings months

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Mine hasn't changed recently, but I guess an update is due sometime soon

You're quite right on both points. The 'published' PR doesn't actually affect your SERPS, it's just a snapshot. There's some good tools on www.iwebtool.com for checking published PR

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