Attribute Modules, or AM, at its core is about defining namespaces for your styles to live in.
<div am-Row>
<div am-Column="12">Full</div>
</div>
<div am-Row>
<div am-Column="4">Thirds</div>
<div am-Column="4">Thirds</div>
<div am-Column="4">Thirds</div>
</div>

[am-Row] { / max-width, clearfixes / }
[am-Column~="1"] { / 1/12th width, floated / }
[am-Column~="2"] { / 1/6th width, floated / }
[am-Column~="3"] { / 1/4th width, floated / }
[am-Column~="4"] { / 1/3rd width, floated / }
[am-Column~="5"] { / 5/12th width, floated / }
/ etc /
[am-Column~="12"] { / 100% width, floated / }