After a quick websearch, as I have not come across this error myself:

One possibility is that there is a problem with the download not being available, another is firewall or security software problems see this article:

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions_-_Firefox#Download_Error_-228

As a trial I just attempted to install this on my computer from https://addons.mozilla.org/en-US/firefox/addon/betterprivacy/

It appears to have installed correctly.

@John99, don't you think that that MozillaLine article is TOO old especially when someone is using Firefox 4 and 5.

@mporter1, Does it happen with other extensions too??? or only with BetterPrivacy???

Hi Swapnilrustagi,

Mozillazine try to keep the KB articles up-to date, they often tend to add updates relating to other versions of Firefox within the same article where relevant. I imagine the article is still doing a good job of explaining Error 228.
If you have any information that is more uptodate I would be glad to see it

Rather more important is that the op is reporting error 288 not error 228

mporter1
perhaps you could confirm the error code you are getting. It may also help if you attach a screenshot of the error. Of course we do not know what is generating the error code, it could be the OS or even another browser.

Thanks, but the problem appears to have resolved itself.

When notified that answers to my question had been posted, I attempted to download and install BetterPrivacy 1.66. It did so without any problem.

Thank you for trying to help. I do appreciate it.

Great, maybe a temporary problem with Firefox at that time.