To quote one URL http://www.googleadservices.com
/pagead/aclk?
sa=L&ai=DChcSEwi36oSzi5fPAhWBh34KHQO2A0YYABAF
&ohost=www.google.com&
cid=CAASJORo9LOCMjoibKPv7gF6cak7OxiE3TtM_
tpkLykYWNps5wdfUw&sig=AOD64_3sHUU366i
6dStUuQ_sGYCNCCiv9A&q=&ved=0ahUKE
wiswYGzi5fPAhVSVWMKHYoQDjQQ0QwIJQ&adurl="
Thats about 300 digits from an alphabet of 0-9a-zA-Z which my computer says allows for "NaN" unique combinations. They could shorten that by 95% percent and still give every atom a unique id.
... and thats just one URL. There are 4 or five more. For three lines of linked text.