Please help me I am getting this screen.
What should I do.
At first it was working fine but after I logged out of the system I got this screen with no option of logging in.
It says page isnt working.
I have changed the hostname of 127.0.0.1 to site4.local and i access the site using site4.local:8000
And this site opens.
OK, so there are 2 aspects here.
your /etc/hosts file would probably contain this
127.0.0.1 localhost
and your ERPNext files/settings would contain something like…
~/frappe-bench/… …/sites/site4.local
If I understand correctly, you edited your /etc/hosts file to change the name of localhost to match the sitename? like so…
127.0.0.1 site4.local
Try restarting the application
bench start
that would be bench restart though
That page is normally displayed when the application is not started up.
First, Have to tried “bench start” instead of “bench restart”?
Second, you will have to put more effort here to help yourself and to allow others to help you. If you post just a screenshot like you did, your responses will be restricted to guess-work, or the experiences of others. If you take the time to view the logs, however, you will find what is really happening. The logs are designed to provide all the detail you require to troubleshoot your application.
@crafter I have started Bench yesterday. I also worked on it and added data to the education module.
But when I open the site again on the browser I get this screen.
Also This is very new to me.
I started from scratch. The installation itself took me 3-4 days.
I am unable to understand ERPNext properly.
For me ERPnext is like handle with care material.
If any slight change is made everything messes up.
That’s ok @Pratik_Vaity. We all start somewhere 
If you are still having a problem, view the logs, and post the relevant parts that you feel might assist.