You want to reference JavaScripts and include links to external CSS files in your web page as simply as possible.

Include script and link declarations, but without the type attribute:

<link rel="stylesheet" href="styles.css" />
<script src="scripts.js"></script>

HTML5 requires only the minimum amount of information needed for user agents. In previous versions of HTML, both CSS links and scripts required the type attribute to indicate the language. If you forgot to include type, though, most browsers assumed the correct value.

HTML5 makes type officially optional, but still validates older documents that do include the attribute. This makes sense, as there is really only one standard scripting language and only one styling language for the Web in use today.