code: public static boolean isValid(final String cssValue) {
          final String trimmedCssValue = TagStringUtil
                  .toLowerCase(StringUtil.strip(cssValue));
  
          final String[] cssValueParts = StringUtil.splitBySpace(trimmedCssValue);
          if (cssValueParts.length > 2) {
              return false;
          }
          if (PREDEFINED_CONSTANTS.contains(trimmedCssValue)) {
              return true;
          }
  
          boolean valid = false;
          for (final String each : cssValueParts) {
              final Object[] lengthValueAndUnit = CssLengthUtil
                      .getLengthValueAsPremitiveAndUnit(each);
              if (lengthValueAndUnit.length != 2) {
                  return false;
              }
              valid = true;
          }
          return valid;
      }
docs: validates if the given cssValue is valid for this class.
  
  @param cssValue
  the value to check.
  @return true if valid and false if invalid.
  @author WFF
  @since 1.0.0