Q:

Is the character "&" alone illegal in HTML 4.01 Strict documents?

I always saw statements to not use & in HTML documents by itself, and use &amp; instead.
So I tried putting & in the title and in the content of the page, but they validate:
http://topics2look.com/code-examples/HTML/ampersand-by-itself-can-validate.html
Is & by itself legal in HTML 4.01 Strict documents?

A:

The W3C HTML 4.01 Strict Charset section says

Four character entity references
  deserve special mention since they are
  frequently used to escape special
  characters:
* "&lt;" represents the < sign.
* "&gt;" represents the > sign.
* "&amp;" represents the & sign.
* "&quot; represents the " mark.

Authors wishing to put the "<"
  character in text should use "<"
  (ASCII decimal 60) to avoid possible
  confusion with the beginning of a tag
  (start tag open delimiter). Similarly,
  authors should use ">" (ASCII
  decimal 62) in text instead of ">" to
  avoid problems with older user agents
  that incorrectly perceive this as the
  end of a tag (tag close delimiter)
  when it appears in quoted attribute
  values.
Authors should use "&amp;" (ASCII
  decimal 38) instead of "&" to avoid
  confusion with the beginning of a
  character reference (entity reference
  open delimiter). Authors should also
  use "&amp;" in attribute values since
  character references are allowed
  within CDATA attribute values.

As it uses the word "should" instead of "must", I guess you can skip it and still validate.  
But don't do  that, because it will sometimes render oddly.
I actually had to escape a couple of the ampersands in my cut-paste of this quote to get SO to render the character entity text... ;-)

