A while back, I was on writing

A while back, I was on writing.com and a download popped up, for js.js, an exe from pixel.mathtag.com. Of course, I didn't download it, and assumed pixel.mathtag.com was just one of writing.com's sponsors. However, it happened again a few days later. This time, I looked up "pixel.mathtag.com" on Google, and found results for Trojans and viruses. Of course. A lot of websites are supported by viruses (MediaFire, AdFly), so I paid it no mind. However, this download just popped up while I was on the FN@F wiki. Is something inside my computer that is doing this?