<script type=text/javascript>
/* ... */
</script>
vs.
<script language=Javascript>
/* ... */
</script>
Which should be used and why?
Or, the third alternative: omitting either of these, such as the example code in jQuery's API reference:
<script src=http://code.jquery.com/jquery-latest.js></script>
The language attribute has been deprecated for a long time, and should not be used.
When W3C was working on HTML5, they discovered all browsers have text/javascript as the default script type, so they standardized it to be the default value. Hence, you don't need type either.
For pages in XHTML 1.0 or HTML 4.01 omitting type is considered invalid. Try validating the following:
<!DOCTYPE html PUBLIC -//W3C//DTD XHTML 1.0 Transitional//EN http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd>
<html xmlns=http://www.w3.org/1999/xhtml xml:lang=en lang=en>
<head>
<script src=http://example.com/test.js></script>
</head>
<body/>
</html>
You will be informed of the following error:
Line 4, Column 41: required attribute type not specified
So if you're a fan of standards, use it. It should have no practical effect, but, when in doubt, may as well go by the spec.
