As regards to tag and attribute names and most keyword-like attribute values,
HTML is case insensitive. You can, for example,
type TITLE or Title or title or even
tItLE if you like.
As an exception, the value of a TYPE attribute in an
OL element is case sensitive.
In this document, upper case letters are used
for the above-mentioned constructs.
This may help the reader
distinguish HTML code from normal text.
The modern trend is to use lower case, and this is a requirement
Beware that the following constructs are (in general)
- escape sequences
(more officially called character entities), which
begin with &
although they may contain parts that are case insensitive,
it is safest to use consistent spelling as regards to case of letters
- other attribute values which are not keyword-like but
strings in general,
such as the value of an ALT attribute
in an IMG element and the value of a
attribute of an A element.
of last update: