I will follow this up. I'm guessing that by clean, you mean no porn. However, your search history, even in a professional context, can say a lot about you.

  1) Search stack traces on google much? You are probably a developer. 

  2) Visit buzzfeed, vice.com, or other news sites, even on your lunch or coffee break? Click on certain stories that might skew to a male audience? 

  3) Have facebook or twitter open? Then you've just handed them the keys to the demographic kingdom.

Believe me, even at work the ad-networks know, at minimum, you are probably male -- hence -- boobs.