A false positive is when there is no malware, but the antivirus still flashes red. I have lost count of the times I have been insulted because of a false positive on software that I presented and which was nevertheless perfectly clean.
Anyway, all that to say that Virus Total now offers an extension for Chrome and Firefox that will automatically scan everything you download with your computer.
It’s a marvelous little extension that will save you a lot of trouble if you like to navigate troubled waters. You can configure it so that it does not analyze documents (which could be confidential), and whether it offers you to do a scan or not.
In short, a great tool to further improve your online security.