* @return The value of found property. (NotNull: if not found, exception but basically no way)
     * @throws NumberFormatException When the property is not integer.
     */
    Integer getThumbnailHtmlImageThumbnailWidthAsInteger();

    /**
     * Get the value for the key 'thumbnail.html.image.thumbnail.height'. <br>
     * The value is, e.g. 100 <br>
     * comment: Height of generated thumbnail images.