After updating the password of user running the Sharepoint applications, you might encounter Error 500 while browsing the sharepoint

You need to update the password on the Sharepoint server in the following places:

• Application pools:
  

Select each of the Application Pools And edit the Advanced Settings to update the account that is used and type new password. Once done, recycle the application pool

• Sites:
  

Select each site individually (including Sharepoint Central Administration and Sharepoint Web Services) and open the advanced Settings, then enter the username and new password and restart the site