Next, choose the "Acconts and Import" tab; move down to "Change account settings" and click on "Other Google Account settings":
Now, choose "Go to web history" from the Services section:
At this point you will again be asked to enter your user name and password:
Finally, click on the box that says "Remove all Web History" which will also "Pause" the collection of website visitation data:
There, you are now more private. Should you ever need those customized ads back, just click on "Resume."