Dangerous globals
This is a common, maybe the first, bad practice but some people are really not afraid about using a lot of globals. IKEA’s devs are those kind of guys. No literals, no namespace, no scope, it works today, why would it fail tomorrow?
<script type="text/javascript" language="JavaScript">
[…]
var width = "Width:";
var height = "Height:";
var length = "Length:"
var cm = "cm";
var kg = "kg";
[…]
This code is from any product page, look at this page for instance, from line 983.