newtabpage still borked
With older versions of FF (e.g. 31) when you opened a new tab you could configure the browser to show you a grid of "favourite" website thumbnails to click on. By default this was set to a 3x3 matrix - but could be changed to show more sites in more rows and/or columns, albeit with smaller thumbnails of each one.
In FF34 this feature was "improved" to fix the grid to 3x3, no matter what about:config parameter the user set. In FF35 Mozilla have applied their infinite wisdom and decided that users should want LARGE thumbnails, rather than to allow the users to choose smaller ones but more of them. So now it *is* possible to have more columns (maybe even more rows, too - but I don't have a screen large enough) but the size of each thumbnail is fixed, irrespective of the size or resolution of the screen I have.