default web site disappeared windows 10

in short: Reinstall both IIS and WAS.

In details -

Step 1

1. Go to "Add remove programs"
2. "Turn windows features on or off"
3. Remove both IIS and WAS (Windows Process Activation Service)
4. Restart the PC

Step 2

1. Go to "Add remove programs"
2. "Turn windows features on or off"
3. Turn on both IIS and WAS (Windows Process Activation Service)

Note: Reinstalling IIS alone won't help. You have to reinstall both IIS and WAS

http://superuser.com/questions/704850/how-to-restore-iis-settings-and-default-web-site