It works fine for me..

Did you disabled your Java or using any Addons/Plugins to disable script?

enable your Javascript in Firefox

• Firefox Orange button > Options > Options > Content

1. [x] Enable Javascript

Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (MAC)

You can remove all data stored in Firefox from a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History > Show All History" or "View > Sidebar > History") or via the about:permissions page.

Using "Forget About This Site" will remove all data stored in Firefox from that domain like bookmarks, cookies, passwords, cache, history, and exceptions, so be cautious and if you have a password or other data from that domain that you do not want to lose then make a note of those passwords and bookmarks.

You can't recover from this 'forget' unless you have a backup of the affected files.

It doesn't have any lasting effect, so if you revisit such a 'forgotten' website then data from that website will be saved once again.

thank you both first of all, the JavaScript is enabled. I observed the following behavior: if i reload the results page with the SHIFT pressed then from there onwards the JavaScript works. But when i start the navigation from scratch(the homepage) it does not unless i refresh the "results" page with the SHIFT pressed then it works - as if the homepage corrupts something?? Consider also that in order to do a trial i did a clean install of the PC and a full update of win 7 x64 then installed firefox(only app installed) and tried pubmed as the first site visited on the PC - same behavior. Similar situation replicates on my laptop.

Any further thoughts?

It is possible that you have security software that is causing problems.

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if that helps.

I did the tests without any security software on. Now the interesting thing is that when i took my laptop (having same problem) to my working place at the University it is fine. I forgot to mention that at home what has changed recently is that i am using as internet at home temporarily my smartphone as a wifi hot spot (android 4.2 - wifi tethering is the app). Don't you think it is unusual to suffer these issues from the internet service coming from the phone?? I guess that must be the only reason. Also the only website affected is this PubMed national library - all other sites are working fine.