Do I need to have a selector name in the same case in css and html?

Question

Do I need to have a selector name in the same case in css and html?

this is normal?

<div id="HEADER"> </div>

#header{...}

or is it necessary?

<div id="HEADER"> </div>

#header{...}

Answer 1

Class names and identifiers are case sensitive, so they must have the same enclosure.

Therefore, div.MyClass does not coincide with div.MyClass.

Element (in HTML) and pseudo-classes (everywhere) are not case sensitive, therefore DIV:hover matches with DIV:hover.

For more information read the spec .

Answer 2

#HEADER {...}, ... , XHTML. . : http://webdesign.about.com/od/css/f/blcssfaqcase.htm