code: public static boolean isValid(final String cssValue) {
          final String trimmedCssValue = StringUtil.convertToSingleSpace(
                  TagStringUtil.toLowerCase(StringUtil.strip(cssValue)));
  
          if (PREDEFINED_CONSTANTS.contains(trimmedCssValue)) {
              return true;
          }
  
          final String[] cssValueParts = StringUtil.splitBySpace(trimmedCssValue);
          if (cssValueParts.length > 5) {
              return false;
          }
  
          if ((cssValue.length() - cssValue.replace(FILL, "").length()) > FILL
                  .length()) {
              return false;
          }
  
          for (final String cssValuePart : cssValueParts) {
              final Object[] lengthValueAndUnit = CssLengthUtil
                      .getLengthValueAndUnit(cssValuePart);
              if (lengthValueAndUnit.length == 0 && !FILL.equals(cssValuePart)) {
                  return false;
              }
          }
          return true;
      }
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