code: public static boolean isValid(final String cssValue) {
  
          final String trimmedCssValue = TagStringUtil
                  .toLowerCase(StringUtil.strip(cssValue));
  
          if (StringUtil.containsSpace(trimmedCssValue)) {
              return false;
          }
  
          for (final CssLengthUnit cssLengthUnit : CssLengthUnit.values()) {
              final String unit = cssLengthUnit.getUnit();
              if (trimmedCssValue.endsWith(unit)) {
                  final String valueOnly = trimmedCssValue.replaceFirst(unit, "");
                  try {
                      // it could be negative
                      Float.parseFloat(valueOnly);
                  } catch (final NumberFormatException e) {
                      break;
                  }
                  return true;
              }
          }
  
          return PREDEFINED_CONSTANTS.contains(trimmedCssValue);
      }
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