How can I report a website for Malware / other Viruses?

I was looking for a new desktop image through google images, and when I clicked on one, a website popped up saying my computer is heavily infected by viruses, spyware, and trojans, and the only way to remove them is to pay for their software, and this website isn't blocked by Firefox in the least, I was wondering, where can I go to report said websites without looking through the site for hours, where I just end up asking everyone else.