I want to say that I have the exact same problem. This website is spawning random ad sites as new tabs in Firefox, Chrome and IE every now and then. It all started after I was infected with the lp.ilivid virus which I was confident Malwarebytes removed, no trace of it anyway. But instead of getting tabs leading to the ilivid website all the time, now I get ad tabs leading to other sites. Search with Malwarebytes, AVG, Kaspersky, Microsoft Scan, SuperAntiSpyware and TDSSKiller all returned negative. I guess I'll have to reformat if it's an impossible-to-find rootkit.