Acer C720 connects to wireless network, but can't load webpages

I am posting this question and answer from
link
because I faced the same problem,
and the solution in that post was helpful to me.

Question from the link:

I have an Acer C720 Chromebook, running a dual boot of Chrome OS and
Ubuntu 14.04.

When using Chrome OS, I can connect to and use private and public
wireless networks with no problems. With Ubuntu, I can also connect to
all networks, but with the vast majority of networks I have tried, I
cannot use the Internet; the standard 'Server Not Found' screen
appears when trying to load up web pages, for example.