Hi !

The setting keyword.URL is no longer supported in Firefox 23, so it will not work even if you have startpage.com there.
Addressbar-searches now uses the default searchengine from the searchbar.
So you have to add startpage.com to the searchbar in order to get startpage back.

Here is a solution: https://startpage.com/eng/download-s...ge-plugin.html

Do not try to install from Firefox's own plugin repository:

as you will get an errormessage saying "You need a Mozilla-based browser like Firefox to install plugins",
even though you are using FF....