code: private void addSeed(SiteNode node) {
  		try {
  			if (!node.isRoot() && node.getHistoryReference() != null) {
  				HttpMessage msg = node.getHistoryReference().getHttpMessage();
  				if (!msg.getResponseHeader().isImage()) {
  					spider.addSeed(msg);
  				}
  			}
  		} catch (Exception e) {
  			log.error("Error while adding seed for Spider scan: " + e.getMessage(), e);
  		}
  	}
docs: Adds the given node as seed, if the corresponding message is not an image.
  
  @param node the node that will be added as seed