When you ask Firefox to open a new tab, Firefox displays a list of top websites of your own history. This list consists of 8 recommended websites placed in one row and named Top Sites.
Their selection is based on your history and are the websites you visit the most. You have the ability to delete a choice of Firefox but its place is automatically taken by the next selection of the program browsing. You also have the ability to drop sites and effectively hide them from the Top Sites entry, as well as rearrange the top sites using drag and drop.
Since Top Sites are quite easy and convenient, let's see how you can increase the number of Firefox suggestions and a series of 8 tiles to make more rows.
First of all, it is quite easy to increase the number of rows to two, as the Mozilla added an option for this job. Clicking on the gear icon in a "New tab" (top right) displays various options. Find among them the option "display two rows" in the area "Top Websites", mark it and a second row will be added to the "Top Websites" when you request a new tab.
However, if the two rows of top websites are not enough for you and you want more rows, Firefox gives you the option and you should take the following steps:
1. Open a new tab and copy-paste it to this address bar:
about: config? filter = browser.newtabpage.activity-stream.topSitesRows
2. On the page that appears, say that you "Accept the risk" and then double-click on name browser.newtabpage.activity-stream.topSitesRows and change the existing value by entering the number with the desired number of rows.
3. Click ok.
Now check out a new tab and you will see the change immediately and, if necessary, modify the number of lines according to your wishes. See below how our selection appears with 4 rows:
