This simply means to use ‘increments of 4’ to size and space out the elements on a page. any defined height or width should be divisible by 4, including padding, margins and line heights.

Consistency is a very important aspect of design to impart a professional outlook to it. imagine in our day-to-day life if we find any part of the online site not consistent with the rest of the experience of that site, it immediately throws us off. therefore it is very important to have a consistent unit of measurement for a layout. A little consistency goes a long way.