Q: Can i upgrade my macbook a1181 to lion?

Read here...

https://discussions.apple.com/message/18758828#18758828

Lion Tech Specs  >  http://support.apple.com/kb/SP629

To Contact Apple in your Country to Purchase a Lion Download code...

http://support.apple.com/kb/HE57

In the US...

1-800-MY-APPLE or 1-800-676-2775

Be sure to make a Backup of your Current System Before Upgrading...

Also... Check here for compatibility of 3rd party Software you may be using...

http://roaringapps.com/apps:table

NOTE that Rosetta is no longer supported in Lion.

You should also consider more RAM... Lion is a hungry beast...

You can use these Links to check which RAM is suitable for your Mac...

http://eshop.macsales.com/shop/apple/memory/

Go to http://www.crucial.com

It is Important to get the Correct and Matching RAM

Those sites also have videos on how to Install RAM should you need it...