HTTP error 404 means the resource being requested from the Web server cannot be accessed. Let's say error 404 appears when going to http://www.example.com.

Try the default documents

If 404 appears when attempting to request a specific page, such as http://www.example.com/page1.aspx, remove the specific page from the URL. In this example, instead of requesting http://www.example.com/page1.aspx, request http://www.example.com. This will tell the Web server to produce one of the default documents. If 404 no longer appears when requesting http://www.example.com, the specific page may no longer be a valid page. The page may have been removed, or the URL to the page may have been changed.

DNS / PING

Using a command line prompt, PowerShell, or Terminal, try to ping the website.

ping www.example.com

If the ping is successful, the IP address of the Web server will be displayed. Enter http://<ip address> in a Web browser. If 404 no longer appears, there is some issue with DNS. Try to visit other websites, such as www.google.com. If you do not need to use an IP address to get to other websites, the DNS issue is not in your network.

When ping is successful, this does not mean the Web server is working properly. The Web server may be completely down, and the Web server may still be able to respond to ping. Likewise, if ping returns request timed out, this does not mean the Web server is down. A hardware firewall, or a software firewall in a router, switch or end point may be configured to refuse all ICMP packets, which will result in a ping request timed out. For this reason, all ping can be used for here is to try to obtain the IP address of the Web server, but not verify if the Web server is up or down.

For Web Server administrators:

• Ensure both ports 80 and 443 are open in your router
• If the port was changed from 80 to another port, such as 8080 in IIS, follow the instructions in the article on how to change the port in IIS.
• If the IP address of the Web server was changed, check the following:
  • Ensure the IP settings of the NIC are updated
  • Ensure the router has the new IP address
  • If using a DNS server, ensure the DNS server has the new IP address
  • If using IIS, in the left panel of IIS, highlight the website, right-click, select Edit Bindings, highlight the Binding, select Edit, and enter the new IP address