code: function consumeNumber(scanner) {
      var value = scanner.consumeNonWS(NUMBER);
  
      for (var i = 0; i < value.length; i++) {
          var code = value.charCodeAt(i);
          if (!isNumber(code) && code !== FULLSTOP) {
              scanner.error('Unsigned number is expected', scanner.tokenStart - value.length + i);
          }
      }
  
      if (Number(value) === 0) {
          scanner.error('Zero number is not allowed', scanner.tokenStart - value.length);
      }
  
      return value;
  }
docs: Terms of <ratio> should to be a positive number (not zero or negative) (see https://drafts.csswg.org/mediaqueries-3/#values) However, -o-min-device-pixel-ratio takes fractional values as a ratio's term and this is using by various sites. Therefore we relax checking on parse to test a term is unsigned number without exponent part. Additional checks may to be applied on lexer validation.