Sometimes ads show up due to cookies your computer collects while browsing other websites. Not to say you were on any racy websites, but they can be picked up from innocent sites like Facebook, Pinterest, couponing sites, etc.
It's definitely a good idea to give a heads up though, but you could also try clearing the cookies and browsing history on your internet browser. You should be able to do that in the options section on the left hand side of the browser screen (if you have a PC computer. Not quite sure how to do it on a Mac, but I'm sure I could find out)
