correct way to include javascript and CSS in XHTML document

[jkd]

If you're using just ECMAscript, then yeah. But extensions like Array.prototype.map or Gecko's getters and setters, that's Javascript (1.5+).

text/javascript isn't official, so you're supposed to use application/x-javascript (but only Mozilla recognizes that mime-type as actual Javascript). So really, you can't be correct. Just go for text/javascript.