If you are using a Linux server, usernames, passwords, and filenames must comply with standard Unix naming conventions.
Username Restrictions
A name of anywhere from 3-16 alphanumeric characters (i.e., the numeric characters 0 - 9 and the alphabetic characters a - z) is legal for email accounts, FTP accounts, and telnet accounts.
Password Restrictions
POP/FTP/Telnet passwords should contain 6 – 8 alphanumeric characters. For the highest level of security, choose a “difficult” password that contains some combination of upper-case and lower-case letters and numerals.
Server File Names
There is no limitation to the length of file names. You can use some punctuation marks in characters in any filename: (e.g. +_-&).
HTML Note: While you can use spaces in your filenames, please note that some versions of Netscape will “throw away” anything after a space. This will result in a “File Not Found” error. Also, the UNIX operating system doesn’t really know what to do with filenames that contain spaces. Therefore, it’s a good idea to avoid the use of spaces in your file names.
HTML Tip: Remember that Unix is case-sensitive. We’ve found that developing the habit of always naming your files in all lower-case avoids a great deal of confusion.