WHO I'VE WORKED WITH
the size of the tab image is 111px by 74px (old) or 170px by 170px. Facebook cover image is 1250px by 630px or the uncommon 851px by 315px (+ 20% bleed).
960px grid is a good size because it has many factors (whole numbers it can be divided into): 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 20, 24, 30, 32, 40, 48, 60, 64, 80, 96, 120, 160, and so on. Being able to divide the grid up in this way provides a lot of flexibility for the width of columns, offering a multi-purpose, reusable grid system.
960px grid is a good size because it has many factors (whole numbers it can be divided into): 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 20, 24, 30, 32, 40, 48, 60, 64, 80, 96, 120, 160, and so on. Being able to divide the grid up in this way provides a lot of flexibility for the width of columns, offering a multi-purpose, reusable grid system.