A couple times this site has tried to deliver a drive-by-download a file called rcpsetup_matomyil_myil442191.exe Up until now I've always had multiple tabs open so I wasn't sure where it came from, though being the internet I suppose there's always a small chance it came from something else. Fortunately I've noticed and cancelled it every time.
Poking around I suspect it's a Malvertisment
Meaning essentially that someone is paying you to distribute malware through your site ads. I'm hoping you can do something about it.
Also if this becomes more of a problem on the internet, maybe you could consider selling an ad free experience as an alternate revenue stream?