When Showing this type error in xampp localhost at running localhost using xampp server. Then First You will go to in file location as below

“C:\Windows\System32\drivers\etc” and open “hosts” file and check this below line

127.0.0.1       localhost
::1             localhostCode language: CSS (css)

After that open file location as below

“C:\xampp\apache\conf\extra” and open “httpd-vhosts.conf” and check below line

<VirtualHost *:80>
	DocumentRoot "C:\xampp\htdocs"
	ServerName localhost
	ServerAlias www.localhost.co
	<Directory "c:/xampp/htdocs">
	Order allow,deny
	Allow from all
</Directory>
</VirtualHost>
Code language: HTML, XML (xml)

if it code will be not available in this file the write this line as below

After update this file will be open your localhost as below