code: function _fnConvertToWidth ( width, parent )
  	{
  		if ( ! width ) {
  			return 0;
  		}
  	
  		var n = $('<div/>')
  			.css( 'width', _fnStringToCss( width ) )
  			.appendTo( parent || document.body );
  	
  		var val = n[0].offsetWidth;
  		n.remove();
  	
  		return val;
  	}
docs: Convert a CSS unit width to pixels (e.g. 2em)
  @param {string} width width to be converted
  @param {node} parent parent to get the with for (required for relative widths) - optional
  @returns {int} width in pixels
  @memberof DataTable#oApi