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Exchange Team Blog inform in post Exchange Server TechNet Library URLs updated that they have updated Exchange TechNet Library URLs.
So now link (http://technet.microsoft.com/en-us/library/bb124558.aspx)) to Exchange 2010 documentation will take you to Exchange Server 2013 documentation.
But if you want to get to Exchange Server 2010 documentation you need only modify this link at the end and add (v=exchg.141) like below:
http://technet.microsoft.com/en-us/library/bb124558(v=exchg.141).aspx
Then you will get to Exchange 2010 documentation on TechNet
It’s not to much work to update your browser shortcuts.
Below you can find links to main documentation for Exchange Server versions:
Exchange Server 2013 Documentation
Exchange Server 2010 Documentation
Exchange Server 2007 Documentation