I guess this explains why I'm having issues connecting to the web or loading webpages.
I scanned my computer with 3 anti-virus softwares and no virus or malwares were found. I noted the threads about people complaining Avast blocking the internet and I used the suggested solution to add the program to the allowed list in Windows Firewall. My internet connection came back but some content on most websites are not loading. I noticed that my internet connection is fully working only when I disable Avast (File Shield and Web Shield). This issue happens with all browsers I tried (Fire fox, Chrome, and Internet Explorer).
Windows 7 64bit, Firefox 40.0.2