Oooops...sorry I forgot to mention how this is related to Lightstreamer

If your Push-pages live inside a frameset, so that Page A is a Push-page that creates the engine with the createEngine method and Page B is another Push-page which wants to get data from the Engine created by Page A, and you have deployed your application in the canonical way (i.e. the web resources coming from a web server and the pushed data coming from Lightstreamer Server) then you should set the domain "by hand" on the frameset file or your app will not work with Opera browsers.

Example frameset:
Code html:
  1. <html>
  2.     <script>
  3.        document.domain = "lightstreamer.com";
  4.     </script>
  5.     <frameset rows="50%,*">
  6.         <frame name="PAGE_A" src="pageA.html">
  7.         <frame name="PAGE_B" src="pageB.html">
  8.     </frameset>
  9. </html>
Page A's javascript snippet
Code javascript:
  1. var lsPage = new PushPage();
  2. lsPage.context.setDomain("lightstreamer.com");
  3. ...
  4. lsPage.createEngine("MyApplication","/LS/","SHARE_SESSION");
Page B's javascript snippet
Code javascript:
  1. var lsPage = new PushPage();
  2. lsPage.context.setDomain("lightstreamer.com");
  3. ...
  4. lsPage.seekEngine("MyApplication", self.parent.frames.PAGE_A);