Skeleton uses standard naming convention each column has two names width of column (one, two, three, four, five,.. ten, eleven, twelve) and the class name columns.
one
This is class = "eleven columns" similar to figure 16-3 page 501
two columns,
This is class = "ten columns", we have class="row" first, a row is a row
three columns
This is class = "nine columns"
four columns
This is class = "eight columns"
five columns
This is class = "seven columns"
this is class = "six columns"
this is class = "twelve columns"
Note container limits the width so you have to go outside class="container" and/or use negative margins/paddings. You also have to set the row div to background:transparent
Standard four columns display class="three columns"
Standard four columns display class="three columns"
Standard four columns display class="three columns"
Standard four columns display class="three columns"

Skeleton provides several short-cut but you need to use column class not columns class with them. Column is implying a single column inside. The short-cuts are: one-third, one-half and two-thirds; they also have offset-by-unit.
Skeleton short cuts ="one-third column"
two-thirds is width 8 units class="two-thirds column"
skeleton short cut class="one-half column"
Skeleton also has offset short cuts, this isclass="offset-by-six four columns"