>>>It seems to be some hide script on your navigator, try to open the levelextreme.com in incognito mode to prevent the issue and/or using other navigator for a while to see if the problem appears again. This will let you know what is going on.
>>>Are you leaving opened the site for days and days? maybe that is also the problem, I never kept opened this site more than 2 consecutive days.
>>
>>I never close it. For years. It's a problem only recently. And my browser is Waterfox, where NoScript simply refuses to work.
>
>Why would you use Waterfox if NoScript won't work with it?

А few months ago Firefox broke the interface to most of old add-ons, practically rewriting its API under different rules. All of a sudden nothing worked. Most of the refugees from FF camp claimed they became like a nanny state, taking care of the problems we didn't have and prescribing the desirable behavior. Waterfox is a fork of the project from the time that corner was turned. All of my old add-ons work. As for NoScript, I haven't really tried it yet, simply forgot :).