Hi, I want to Install "mosaic" Add-on I did this as I usually do but when I enter to my Site Setup => Add-ons I do not see the Install button next to "mosaic" Add-on and appears to me "Warning This product cannot be uninstalled!" Message?? any help ?
You can ignore this unless you are about to install it on a live production site and you have not tested it before on a development site. Some add-ons do not include an uninstall "profile". Uninstall profiles, in theory, take care of removing all traces of the add-on if you ever decide to uninstall them.
This is because something in your buildout did not work correctly. As Andreas hints subtly, please provide us with more information about your Plone version, the Mosaic version you're trying to use, the buildout.cfg file, the command you ran buildout with, and the output of the buildout run.