Avast Web Shield has blocked a harmful webpage or file

Avast Free Antivirus / Premium Security
1

I get this popup every 20 seconds while I browse internet and it’s become really annoying:

http://i.imgur.com/q7EK23E.png

How can I prevent it from showing up?

2

Attach your basic diagnostic logs. (MBAM, FRST and aswMBR)
Instructions: https://forum.avast.com/index.php?topic=53253.0