:The suggested format as below of the username worked ok
1. Put local host in "Host name or IP address" field
2. put domain name\username in username field
3. keep the "Domain" field as blank(please do not fill anything)
4. Check the "Windows" check box
Note: If windows authentication is enabled on IIS server then user must provide user & password in windows authentication section. Option 2
: anonymous authentication not enabled - by setting this in IIS, the domain name entry is no longer required
Anonymous access should be there on IIS server
Anonymous access, the most common web site access control method, allows anyone to visit the public areas of a web site while preventing unauthorized users from gaining access to a web server's critical administrative features and private information. Anonymous authentication gives users access to a web site without prompting them for a user name or password. When a user attempts to connect to a public web site, the web server assigns the user to the Windows user account called IUSR_computername, where computer name is the name of the server on which IIS is running.
For more details please follow this url:https://helpx.adobe.com/dreamweaver/kb/anonymous-authentication-iusr-account.html
Also can check if anonymous-authentication is enabled on server where IIS is installed and enable is not already enabled
1. Go to control panel
2. Go to administrative tools.
3. Click on IIS Admin
4. Find the website.
5. Click on Authentication.
6. Enable Anonymous Authentication.
7. Restart the website.