1. Characters you can use safely

Use only the following ASCII characters for your identifiers, variables, and functions names.


The beauty about the old-fashioned ASCII character set is:

It is available on any computer platform in any country in any language setup.

Even though current standards allow to use a wider set of characters in many cases restricting this to the subset above avoids problems with older or badly configured operating systems, servers and browser or different regional/language setups.


2. Case-Sensitivity

Most identifiers are case-sensitive according to the language specification, that means “Web-site” is different from “web-site”. Some are not for example note in particular that element names are case-insensitive in HTML, but case-sensitive in XML.

To avoid potential problems and ambiguity type the identifiers always in exact case, but treat them as they were case-insensitive. I.e. don't use “Manual” and “manual” as separate identifiers. You might mix them up to easily and “buggy” software might mix them up, too.


3. HTML, XHTML ID and NAME Tokens

E.g.:

• No spaces
• Must begin with a letter [A-Za-z]
• And may be followed by any number of letters [A-Za-z] , digits [0-9], hyphens "-", underscores "_", colons ":", and periods ".".

4. CSS Class Names

HTML:

CSS:

• No spaces
• First Character must be a letter [A-Za-z]
• Allowed are Letters, Numbers, Underscores, and hyphen [A-Za-Z0-9] + [_] + [-]
• Case-sensitive in XML, "WebSite" is not "website"
• Case-insensitive in HTML, however type exact case, but treat it as it were case-insensitive
• Multiple class names are delimited by a whitespace [ ] character.
• Descriptive, but keep it short (even though there is no upper limit for length defined)

5. Variable and Function Names

in PERL, PHP, JavaScript

• no spaces
• [A-Za-z0-9] + [_], no "-", ".", ":"
• Case-sensitive
• Must begin with [A-Za-z] or [_], no digits up-front
• Must not be a reserved word of the language
• Descriptive, but short
• You must not use any reserved word

Reserved words for JavaScript:


Lookup the reserved words for PERL (↑) and PHP (↑) in the corresponding documentation.

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Other References: W3C (↑) – The World Wide Web Consortium

Happy coding.
John W. Furst