Can I get a virus on Android 4.4.2 by clicking "no thanks" on one of those virus browser pop-ups?
Well it's hard to know. Install avast anti-virus from google play and it will show any viruses (if there are any). But that 'Message Box' shouldn't have appeared, so that means either Facebook was hacked or you were using a fake Facebook app/page. Clicking 'No Thanks' on a webpage can't install anything unless you already have a virus on your Android. You should be safe if you were using the genuine Facebook app/page and that Settings&gt;Security&gt;Unknown Sources was unchecked.