you right google don't know bzu pages chatting, private messages and other sites but I've told you that google knows all our activities which we do on net.
dear admin google knows what is you browser history and cache knows.....
even if you delete your browsing history. when you search on your system and if you search the same keyword on the private browser there may be different results because in search google shows you the sites which are most relevant to your recently searches.
you can test it...
search an odd topic which you never search on your system for example search the gas generators prices etc. after browsing 30,40 mins for gas generators open different sites which are not related to gas generators, you would probably see the generator ads on that sites...it is because google knows what you are searching and google shows relative ads to you ....
did you get my point .......

---------- Post added at 04:19 PM ---------- Previous post was at 04:18 PM ----------

the word chatting i've used earlier its really misleading. but by this I mean to say the chatting sites that we use..

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Punjab University Lahore
Website Designing in Pakistan