Q:

Unable to create new web application

When I try to create a new web application, it just shows message as 'This should'nt take too long'.. Then, after a while it will show message as Request Timed Out.
Sometimes it will show 'this page could not be found' web page.
Sometimes it will show 'this page could not be found' web page, however, when I come back to manage web app screen, I can see that the web app is created.
What do you think is reason for these 3 cases above?

A:

I had the same problem just a couple of days ago. Do you run many web-applications in your farm? From the blogpost:
This is usually because you either have too many Web Applications in your SharePoint Server, or because your SharePoint Server is slow! As part of the Web Application creation process, SharePoint resets IIS. By Default, the application pool only allows for 90 seconds for all the connections to close before it down by force. If you got this message it’s because 90 seconds wasn’t enough and we need to increase that limit.
I found the solution here, and it worked perfectly. Go into IIS and change the property "shutdown time limit" for the central admin application pool from 90 to 300 seconds.
Internet Explorer cannot display the webpage when creating new Web Application in SharePoint 2013

