void analyzeFrame(String frame) {

	String src = extract(frame, "src");
	//    if (src == null) System.err.println("src null");
	if (src == null) return;
	try {
	    //	System.err.println("in analyzeFrame: adding " + base + "|" +
	    //	src);
	    addURL(new URL(base, src));
	} catch (MalformedURLException e) {
	    //	    e.printStackTrace();
	}
    }