Sharepoint - Can't pass authentication to browse a sharepoint site

• Check, or double check, if the loopback check is disabled
• Check if you can log in from your client pc instead of logging in from the server
• Disable "enhanced security" of the IE on the server (for test purposes only) and try it again
• Add SharePoint site to the intranet zone in IE
• Log in with "the other user" and check the permissions of your account (like it is done here: http://teamcollab.wordpress.com/2010/01/25/checking-permissions-in-sharepoint-2010/)

I had this same issue, and I am not sure what I changed that caused this to happen. After I first installed SharePoint it was working, then after modifying a lot of things, it stopped working.

How I fixed this very frustrating issue.

1. First I logged into the SharePoint server and ran the SharePoint 2013 Products Configuration Wizard.
2. Next I went to Central Administration. Under Application Management click on Manage web applications.
3. Highlight SharePoint - 80 and click on Application Providers from the ribbon menu. Click on Default.
4. Scroll down to Integrated Windows Authentication and change the setting from Negotiate (Kerberos) to NTLM.
5. Click on Save. Close this popup window.
6. Next with SharePoint - 80 still selected click on User Policy. Add a user or edit the user in the list and set the proper permissions.