function _fnStringToCss(s) {
		if (s === null) {
			return '0px';
		}

		if (typeof s == 'number') {
			return s < 0 ?
				'0px' :
				s + 'px';
		}

		// Check it has a unit character already
		return s.match(/\d$/) ?
			s + 'px' :
			s;
	}
Append a CSS unit (only if required) to a string
 @param {string} value to css-ify
 @returns {string} value with css unit
 @memberof DataTable#oApi