HTML index
Every website is built inside directories on a Web server. And each Web page is a separate file on that Web server. But sometimes, when you go to a URL, there is no file listed in the URL. For example: http://www.webgrid.com But there is still a file that the Web server needs to serve in order for that URL to display anything other than an error page. This file is the default page for that directory. On most Web servers, the default page in a directory is named "index.html".