@-moz-document url(about:newtab)
{
/* Fix cell sizing. Note: you may need to play around with the values for different numbers of rows and columns */
/* Currently it works for 3 rows x 4 columns */
.newtab-cell { width: 19% !important; height: 25% !important; }
/* Fix grid sizing */
#newtab-grid { max-height: none !important; max-width: none !important; overflow: auto !important; margin: 50%; }
/* Hide unnecessary elements */
#newtab-search-container, #newtab-search-logo, #newtab-margin-top, #newtab-margin-bottom, #newtab-intro-what, .newtab-side-margin, #newtab-customize-button, .newtab-undo-container { display:none !important; }
}

#newtab-scrollbox {
  margin: auto !important;
}