Just a notice.
In Fx 3, and perhaps older versions, when you open the “Library” to manage your bookmarks, Bookmarks | Organize Bookmarks, and select a bookmark by single clicking on it (left or right), Firefox makes a quick connection to the site that holds the page you have bookmarked. Odd, since you do not open the page by double-clicking or right-clicking and select another tab etc, you just point and click, as one many times does before a right-click operation.
The same thing happens when you right-click and select Properties for a bookmark from inside the browser, Bookmarks menu.
Perhaps there is a reason, update “favicons” whatever, but I do not see that happen and if the address is not valid you don’t get any feedback in Fx anyhow, unless of course you try to open the page.
However, the above is shown by TCPView from Sysinternals/Microsoft, as shown in the screen shot.
So, for anyone who wants to manage their bookmarks inconspicuously, perhaps I may propose Offline mode. 
