...
var dp = Components. classes ["@mozilla.org/xmlextras/domparser;1"].
             createInstance (Components. interfaces. nsIDOMParser);
var doc = dp. parseFromString (string, "application/xhtml+xml");
var header = doc. documentElement. getElementsByTagName ("head") [0];
var body = doc. documentElement. getElementsByTagName ("body") [0];
...

var _iframe;

function parse(htmlText)
{
    // Find a window to stick our hidden iframe into.
    var windowMediator = Cc['@mozilla.org/appshell/window-mediator;1'].
                         getService(Ci.nsIWindowMediator);
    var window = windowMediator.getMostRecentWindow("navigator:browser");
    // XXX We can use other windows, too, so perhaps we should try to get
    // some other window if there's no browser window open.  Perhaps we should
    // even prefer other windows, since there's less chance of any browser
    // window machinery like throbbers treating our load like one initiated
    // by the user.
    if (!window) {
      var icon = document.getElementById('adslpanel');
      icon.setAttribute("status", "failed");
      icon.label = "failed";
      return;
    }
    var document = window.document;
    var rootElement = document.documentElement;
  
    if (_iframe) {
       if (_iframe && _iframe.parentNode)
         _iframe.parentNode.removeChild(_iframe);
       _iframe = null;
    }

  
    // Create an iframe, make it hidden, and secure it against untrusted content.
    _iframe = document.createElement('iframe');
    _iframe.setAttribute("collapsed", true);
    _iframe.setAttribute("type", "content");
  
    // Insert the iframe into the window, creating the doc shell.
    rootElement.appendChild(_iframe);

    // When we insert the iframe into the window, it immediately starts loading
    // about:blank, which we don't need and could even hurt us (for example
    // by triggering bugs like bug 344305), so cancel that load.
    var webNav = _iframe.docShell.QueryInterface(Ci.nsIWebNavigation);
    webNav.stop(Ci.nsIWebNavigation.STOP_NETWORK);

    // Turn off JavaScript and auth dialogs for security and other things
    // to reduce network load.
    // XXX We should also turn off CSS.
    _iframe.docShell.allowJavascript = false;
    _iframe.docShell.allowAuth = false;
    _iframe.docShell.allowPlugins = false;
    _iframe.docShell.allowMetaRedirects = false;
    _iframe.docShell.allowSubframes = false;
    _iframe.docShell.allowImages = false;
    
    // Convert the HTML text into an input stream.
    var converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"].
                    createInstance(Ci.nsIScriptableUnicodeConverter);
    converter.charset = "windows-1251";
    var stream = converter.convertToInputStream(htmlText);
    
    // Set up a channel to load the input stream.
    var channel = Cc["@mozilla.org/network/input-stream-channel;1"].
                  createInstance(Ci.nsIInputStreamChannel);
    var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
              
                  
    channel.setURI(ios.newURI("https://www.example.by/", "windows-1251",null));
    channel.contentStream = stream;
    
    // Load in the background so we don't trigger web progress listeners.
    var request = channel.QueryInterface(Ci.nsIRequest);
    request.loadFlags |= Ci.nsIRequest.LOAD_BACKGROUND;

    // Specify the content type since we're not loading content from a server,
    // so it won't get specified for us, and if we don't specify it ourselves,
    // then Firefox will prompt the user to download content of "unknown type".
    var baseChannel = channel.QueryInterface(Ci.nsIChannel);
    baseChannel.contentType = "text/html";

    // Load as UTF-8, which it'll always be, because XMLHttpRequest converts
    // the text (i.e. XMLHTTPRequest.responseText) from its original charset
    // to UTF-16, then the string input stream component converts it to UTF-8.
    baseChannel.contentCharset = "UTF-8";
    
    // Register the parse handler as a load event listener and start the load.
    // Listen for "DOMContentLoaded" instead of "load" because background loads
    // don't fire "load" events.
    _iframe.addEventListener("DOMContentLoaded", parseHandler1, true);

    var uriLoader = Cc["@mozilla.org/uriloader;1"].getService(Ci.nsIURILoader);
    uriLoader.openURI(channel, true, _iframe.docShell);
}

  function parseHandler1(event)
  {
    alert(_iframe.contentDocument.getElementsByTagName("table")[11].innerHTML);
    //event.target.removeEventListener("DOMContentLoaded", this, false);
  }