can a mac os x 10.6.8 be safely be upgraded to ocx10.7

Yes, if it has at least a Core 2 Duo(not Core Duo) CPU and 2GB of RAM. Back up your data and check your applications for compatibility first.

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Yes, if your computer meets the system requirements and you back up the content first.

System requirements for OS X Lion and Mac OS X v10.6 - http://support.apple.com/kb/HT4949

Kappy, April 2014 post - Upgrading from Snow Leopard to Lion or Mavericks - https://discussions.apple.com/thread/6068376?answerId=25407929022#25407929022