C'mon, it's CSS, you can easily remove that line with the textarea declaration and you're done leaving it to whatever is used by a browser. Or make it all serif, it's that easy.

Don't know why you're getting downvoted: the author explicitly encourages the file not to be used as is but modified to suit your purpose.

I don't see many textareas sized by row/col attributes anymore. Usually they're set to an explicit height and width.

Rows and columns became meaningless and outdated the moment browsers added those little grabbers in the corners.