The following procedure will help you to understand the file requirements.
Your website's hosting control panel username and password.
 Files must be named in lower case only [ Example : index.html NOT AS "INDEX.HTML" OR " Index.html"]
 Space should not be given between words while naming the files [ Example : emailhelp.html NOT AS email help.html ]
 Avoid lengthy file names.
[ ! Notes ]
Always name the files with proper logic.
Avoid renaming the files in the server.
Few files might not be renamed in the server due to sharing violations