one row will divide to the number of parts, if you just set class='c'
on large screens if you just set class='x', it will take the x class ratio
three equal parts
sum of parts is 12, every part will take ratio of it's class number
it will take just 6 part of 12
float right boxes, by .os class
Responsive on medium devices, like tablet's by .m classes
Responsive on mobile devices by .s classes