Alright, speaking from experience here.....
When you come home, and your S.O. instantly minimizes the browser window, and then does everything possible to distract you from the computer so you don't see the name of the site in the toolbar.
And then when you DO see it, claims he's just reading profiles, and that he accidentally
was directed to the personals website while he was looking for p0rn.
And then the big one.... when you go to log into your Yahoo mail on his laptop, and the Windows "Forms" function is active, and it automatically fills in a login name, which is similar
to his normal email address, but just a little different and incorporates his middle name and his son's birthdate) but when asked about it, says, "Oh, I took my laptop to work, one of the guys at work must have logged into his mail."