In case any one is interested, I seen an article yesterday about how Facebook, Google and Twitter can track you browsing other websites.
I use NoScript and do not even allow twitter to script nor do I have an account but, earlier I seen where 20 attempts from twitter had been blocked by the addon.
Here is the solution: install "facebook disconnect", "google disconnect" and "twitter disconnect" addons to Firefox.
EDIT: When you search for the first one in Firefox addons, the other 2 will be on the same page.
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