Why it is Important to Keep Your Site Clean of Unnecessary Embellishments

One can write standards-compliant sites that are full of Javascript games, Dynamic HTML, and other monsters like that. It is usually a bad idea.
Getting Javascript code to work properly on all browsers is more difficult than getting a static HTML to do so. (or at least it can never be easier).
Most Javascript code is unnecessary. It adds more gizmos to the site, but not more functionality.
By adding unnecessary embellishments to the site, you make them more prone to browser bugs, and mis-features; you make the site harder (and more costy) to maintain and you usually don't add much to the user experience to be worth it.
An extreme example of this are pages that use HTML 4.x markup without any CSS or other visual embelishments. If you do this, I guarantee you that your portability problems are over.
( I wouldn't recommend this extreme, because it will make your pages quite boring, but it still illustrates a point. )

7.3. Why it is Important to Keep Your Site Clean of Unnecessary Embellishments