Firefox Can't Access Certain Sites, But Other Browser Can

When i'm connected to a public wifi, In my case, i can't access google.com, skyscrapercity.org, youtube, and even this blog. But when i open google chrome, the website loads well. But firefox are really a browser that i comfortable with, so i have to figure out for the solution.
Fixes :

1. Try to clear the history in firefox, History>Clear Recent History>Everything, Clear Now. (note : cookies will be cleared, at next you will need to relogin to every websites)
2. Disable the DNS prefetching, type about:config in firefox address bar and press enter, Click "I'll be careful, I promise!", then search for "network.dns.disablePrefetch", right-clik and choose toggle to switch the value to "true".  skip to step 3, i found that disabling IPv6 is enough to solve the problem.
3. Disable IPv6 in Firefox, continuing the previous step, still on the same page (about:config), search for "network.dns.disableIPv6", then set it to true. 
4. Refresh the sites, problem should be fixed.

Source : 
https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can 
https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors#w_the-problem-only-happens-with-certain-websites