Here's another one. Pretty common place, I'd think.
I remember sitting around up in my room playing PS2 or something, at the age of 14, when I heard a not quite pleased parental voice blast up the stairs. Knowing that usually came before a nice "I'm ****ed" scenario, I sighed and paused my game, heading out to face the music as it were.
I came down to find my Mom and Stepdad standing in front of the family computer with the most pissed off expression I think I'd ever seen on either of them up 'till that point. You can't see the monitor from the hall, but I knew damn well what it was about. My mom looked at me with what I thought was a mix between confusion and murderous rage, exclaiming, "What in the hell is this!?"
Now, you see, I've always been able to think on my feet when it comes to stretching the truth, and it didn't take me more than a few seconds to realize what was happening and come up with a viable explanation for it. I feigned confusion of my own, I'm pretty good at faking emotion for the sake of a lie, and walked over to get a view before talking...didn't want to start railing about something without knowing exactly what was going on. On the screen was a beautiful young brunette, butt-naked, legs spread wiiiiide. I suppressed a grin.
Still maintaining my composure and outer confusion, I said, "You've got to be kidding me...that god damn Gamespy site!"
They exchanged glances, both unbelieving, then asked, "What site?"
"That Gamespy site must have uploaded a dialer/cookie when I was searching on it. God, they do it all the time. I thought the firewall was keeping that crap out."
Lucky for me, neither were, or are, computer literate, so I was able to bull**** them into believing that and thought I was getting away, completely unharmed, but then they noticed the history folder.......Needless to say, lots of screaming, stammered apologies, and an eventual grounding from the internet for a month or two.
I learned pretty quickly to empty that damn folder and adjust every setting available in IE to cover my tracks in the future.
Like I said. Common thing.