[aembleton]

I've changed the `browser.newtabpage.activity-stream.topSitesCount` to 36 which fills my screen with 6x6 boxes filled with my top sites. Except, for the last box which is always empty!

It seems that there is a hard limit in Firefox of 35 top sites.

[ChrisSD]

Did you try restarting your browser? I've just tried setting rows to 12, which sets topSitesCount to 72. This worked for me after restarting the browser.