Sigma object registration is not removed after the HTML page is shut down.
Sigma Server (all)
The Sigma HTML applet can not send a de-register indication when the HTML page is closed down.
When the HTML page is closed down the registered objects are de-registered after about 5 minutes.
The process for the HTML applet is different to a normal graphic update as it relies on the applet to poll the Sigma server. The poll interval (ms) is determined by the applet parameter
<PARAM NAME="refresh" VALUE="5000">
Once this stops then the Sigma server will time out and de-register the objects in the controller.