Error: The requested URL "[no URL]", is invalid

I am trying to access certain websites, for instance http://ift.tt/1ykEjuh . However, I keep getting the following error: Invalid URL

The requested URL "[no URL]", is invalid. Reference #9.7c2e12d1.1474828790.d54aa8b

Why is this? This happens sometimes with Stackoverflow, Facebook, etc. I looked through many questions and couldn't find a working solution. I am not even sure what exactly is going on. I tried flushing the DNS cache, but that didn't fix anything. I read it could be a php problem. But I'm not convinced of that, because other sites are not working either. The website seems to work completely fine, and then suddenly, when I refresh the page, it shows me that error and persists for a good few hours.