This is not a problem with the site.

The Java Deployment Toolkit was reported vulnerable by Java. There hasn't been a update for the Toolkit yet.

Java recommends disabling this plugin, via the Firefox plugin manager.

I have attached a screenshot of how to disable the plugin for the Firefox plugin manager.

ComputerWhiz, thank you for your answer. My question was not about this pop-up appearing, my question is about behavior of this pop-up... why does it move my menu bar from the top of the page to the middle? At the current moment, I have found that this pop-up is added by FireFox to the first div tag of the page... According to my code, application's panel is described at the first div tag. Menu bar is the second div tag... As I've found in css, menu bar has 'position: relative' style. So It seems to be the rootcause.

When I get this problem fixed, I will confirm what is the rootcause

I am unsure what is causing the issue.

It is most likely just an issue in the CSS programming for that website.

I hope you are able to find the issue soon.

Please report back soon.

ComputerWhiz, yes, it was CSS issue. This site uses ExtJs library and menu bar is 'panel' in ExtJs. Default CSS for ExtJs panels has 'position: relative'. When this pop-up appears, FF put it at the first div tag and that is why menu bar is redrawn. I have tried 1) to override 'position' from 'relative' to 'absolute' 2) to add into css 'z-index=9999' (with 'opacity= .99' to get z-index applied) but it has been all in vain.

So the fix was changing 'position' from 'relative' to 'fixed' with adding the following fields: 'top: 1px; right: 1px' (left top corner).