Directory Index Hierarchy (UNIX Servers)
The Directory Index Hierarchy is the naming order Web servers use to load your home page files.

For example, if you place two home pages on the server, one named "Welcome.html" and the other named "index.html", the Web server will load "Welcome.html" as your home page. The Directory Index Hierarchy for UNIX servers is:

The following names are case sensitive.

index.php
index.php4
index.html
index.htm
index.shtml