In HTML, there are two characters that demand special treatment: <
and &. Left angle brackets are used to start tags; ampersands are
used to denote HTML entities. If you want to use them as literal
characters, you must escape them as entities, e.g. <, and
&.
Ampersands in particular are bedeviling for web writers. If you want to
write about 'AT&T', you need to write 'AT&T'. You even need to
escape ampersands within URLs. Thus, if you want to link to:
http://images.google.com/images?num=30&q=larry+bird
you need to encode the URL as:
http://images.google.com/images?num=30&q=larry+bird
in your anchor tag href attribute. Needless to say, this is easy to
forget, and is probably the single most common source of HTML validation
errors in otherwise well-marked-up web sites.
Markdown allows you to use these characters naturally, taking care of
all the necessary escaping for you. If you use an ampersand as part of
an HTML entity, it remains unchanged; otherwise it will be translated
into &.
So, if you want to include a copyright symbol in your article, you can write:
©
and Markdown will leave it alone. But if you write:
AT&T
Markdown will translate it to:
AT&T
Similarly, because Markdown supports inline HTML, if you use angle brackets as delimiters for HTML tags, Markdown will treat them as such. But if you write:
4 < 5
Markdown will translate it to:
4 < 5
However, inside Markdown code spans and blocks, angle brackets and
ampersands are always encoded automatically. This makes it easy to use
Markdown to write about HTML code. (As opposed to raw HTML, which is a
terrible format for writing about HTML syntax, because every single <
and & in your example code needs to be escaped.)