Make everything box-sizing: border-box;

You probably already implemented a similar rule to this but might forgot to add pseudo-classes. They need to be separately triggered to work within browsers.
Now update your code, be a framework, a grid system or just your personal site and save more time:

*, *:before, *:after
{
    -webkit-box-sizing: border-box;
       -moz-box-sizing: border-box;
            box-sizing: border-box; 
}