It is surprising how much objects can compress. Harold Edgerton, the person who pioneered high speed photography has some interesting examples of compressed objects getting hit hard (all shot with high speed cameras in the pre-digital age)
I don't think a single rogue ad is responsible for this, I think you're the victim of a scripting attack. I'm not sure what blog app you are using but there are a number of ways for a malicious person to sneak a script into part of your site and do a number of nasty things.
In your case I think you are being hijacked by an advertising script that is simply putting the ads it wants onto your site, taking advantage of your traffic. During a visit to your site last night I got a security warning from a security app I run that detected that a known domain that hosts malware was being called from your site.
http://tinyurl.com/3y572oe
http://tinyurl.com/3xanr6j
In your case I think you are being hijacked by an advertising script that is simply putting the ads it wants onto your site, taking advantage of your traffic. During a visit to your site last night I got a security warning from a security app I run that detected that a known domain that hosts malware was being called from your site.