Repeated CSS rules for .grid-system and .row

[njsfield]

The grid-system css class and row css class share the same declarations (width: 100%, max-width: 500px), except grid-system also applies 'margin: auto'. These classes are both applied on html elements.

It may be clearer to use one .row class on all section elements, and for the whole container use a class called 'center', which simply applies a 'margin: auto' rule