It is a well known bug with the 10.6.8 Mac App Store update that after it is installed, 10.6, will popup occasionally and advertise Mavericks update existence.
This update may already be installed for those with 10.6.8 preinstalled.
It has been found the best way to fix this problem is to delete two files. Before you do so, move any important files out of the trash into their own folder on the desktop or your Home folder. Next here is the full path to the two files:
Administrative access may be required to delete them. Use the Go menu to get to the folder:
Click once on Noticeboard.app and select Get Info from the file menu on Noticeboard.app alone, and change ownership and permissions to allow you to read/write the file. Then drag to the trash and force empty trash from the Finder menu.
And do the same with:
(in neither case are you dragging any other content from those folders except the boldfaced file mentioned).
As a consequence of doing this, you will no longer see any notices of updates that are pending through the App Store, unless you go directly to the Mac App Store application. Alternatively you can move the files to a place for your safe keeping, if you write down how the permissions are set before you change them.
It is strongly recommended you read this tip before updating to 10.7 or later:
Another way to remove it may be to extract the old version of the Mac App Store program using http://www.charlessoft.com/ Pacifist from the 10.6.8 combo update, although this may make the App Store itself less secure:
Alternatively, you can temporarily disable the store entirely by compressing it in a zip file.
I would if you are experiencing this problem let Apple know about it, so they can offer alternatives.
or if you have a bug report, signup for the online developer account at http://developer.apple.com/ and submit it here: