According to Norton's Safe Web website:
Norton Safe Web is a new reputation service from Symantec. Our servers analyze Web sites to see how they will affect you and your computer. Then, using the Norton Toolbar installed on your PC, we let you know how safe a particular Web site might be before you view it. If you need to find out more about how a Web site might behave, we provide more detailed information right here on Norton Safe Web.
To do this, the toolbar has to send the website to Symantec, which then replies with the "safety level", and the toolbar inserts the rating icons on the page. Surprisingly, I can't find any information about what information the toolbar is sending to Norton.
If you don't like the extension, you can always uninstall the Safe Web software, or remove the toolbar from Firefox. Firefox includes it's own malicious content checking (as does Google's search results).
For what it's worth, I much prefer using Microsoft's Security Essentials antivirus/anti-malware over Norton. Security Essentials is quiet and unobtrusive, and so far it's caught everything the web's had to send at me.
Edit:
I just tried to install the Norton Safe Web Lite toolbar (the free version), and I was able to see (but not copy/paste...) the license agreement, which has a rather large section on privacy. I imagine it's the same or very similar to what you "agreed" to by having their software pre-installed on your laptop.
Click for the full-size version
Well, until now I cannot see a solution that matches all 5 mandatory requirements...
But I think I'll give up searching - at least until someone post a best answer.
With the help of @avirk and testing translating other pages with mentioned tools, I re-analysed them and took some decisions...
Palliative Solution 1:
To use FlagFox add-on
In which cases?
For sites that not require authentication (HTTPS), form posting, scripts... So you can configure FlagFox to translate page at 1 mouse click on flag; you should do it once and every link pressed (with mentioned limitations) will access its translated page.
Why?
It does not support some scripts, form posts and HTTPS, so you can use that to navigate in sites like Wikipedia, news etc. (but you cannot edit wikis, post comments, share news on social networks...).
It matches requirements?
No at all (2.5 of 5 mandatory points):
1. Translate pages automatically after entering URL;
-> Unchecked.
2. Display of the page would be as in original language (links, images, flash
contents... would not be affected);
-> Checked partially: Inside HTTPS pages or pages that require some scripts, it would not show it as in normal navigation.
3. Linked pages must be also translated;
-> Checked: Well, since linked pages are not HTTPS or require some script or form posting, it will function perfectly! You must only mouse click once on first page.
4. Other browser operations must not be affected (e.g. posting forms,
downloading etc.).
-> Unchecked: As said in 2 and 3.
5. Firefox solution (I hate IE, Chrome, Opera, Safari and all others than
Firefox, but I accept also a general solution but that function on
Firefox).
-> Checked.
Palliative Solution 2:
To use Google Translator Script Bar
In which cases?
For sites that requires authentication (the cases that solution 1 does not cover).
Why?
It supports some scripts, form posts and HTTPS, but with that you must do that annoying thing to press bookmark on every new link pressed...
It matches requirements?
No at all (2.5 of 5 mandatory points):
1. Translate pages automatically after entering URL;
-> Unchecked.
2. Display of the page would be as in original language (links, images, flash
contents... would not be affected);
-> Checked: And it is so good!
3. Linked pages must be also translated;
-> Unchecked: :(
4. Other browser operations must not be affected (e.g. posting forms,
downloading etc.).
-> Checked partially: It launches some Google error messages for some downloads;
5. Firefox solution (I hate IE, Chrome, Opera, Safari and all others than
Firefox, but I accept also a general solution but that function on
Firefox).
-> Checked.
Summarizing:
- Palliative Solutions 1 and 2 can do the work well, but with some restrictions (and do not cover optional requirements);
- What would be a better solution (what matches requirements):
- An add-on (or something like that, GreaseMonkey perhaps), that uses Google Translator Script Bar (or similar) on every page, just inserting an URL on address bar and entering it, without the need of pressing a button after the page is already loaded;
- It would be nice to have in it a button to enable/disable toggle and some kind of blacklist/whitelist (= optional requirements mentioned).
Best Answer
You are getting an up to date list of blacklisted URLs that are known to contain phishing and malware. The update happens shortly after startup and once again every 30-45 minutes.
Mozilla claims the following:
The accepted answer here is unfortunately completely wrong, as this feature can absolutely be disabled easily.
Despite what it says, none of the messing with the hosts file is necessary, you can just change the "Block reported attack sites" and "Block reported web forgeries" settings in Firefox's Security Preferences and this will stop both the updates and checking the lists from happening.
If you manually fiddle in the about:config settings, you must also flip this preference: "browser.safebrowsing.downloads.enabled" which disables updating of blacklisted downloads as well.
Mozilla claims that no information about search queries is ever sent, only the double-check of an encountered reported phishing or malware site, as mentioned above.