Seriously? Col is too difficult to understand as an abbreviation for column?

It takes longer to parse. The same way "Wht r u talking abt" takes longer to parse than "What are you talking about". The former requires my brain to do several extra lookups before I arrive at the meaning. I would rather just type the extra characters for the words Column and Large.

After you've typed a thousand of these things your brain will just be doing a single lookup. From a newbie perspective, your opinion has merit but for long-term use it makes less sense.

Long term, making sure people use proper names for things is a great to make sure people are writing code for others to read.

Skeleton's also nice at this:

    class="six columns"

You can also do wildcard selecting with the namespaced approach. E.g.:

    [class^="col"] { /* blah */ }

class="marketing" is even better.

Then you put your styling in a style sheet.

You use border box by default since it's 2015, the parent uses flex, and set the width to 50%.