Hi Roman, jsFiddle is great for minimal examples. :)
As far as I know, you can't actually extend Element in Internet Explorer. What MooTools does is essentially a bit of jiggery-hackery: when you get an element using document.id() (or its cousins), various properties are added to the element (in the DOM) that provide you with access to the various Element extensions. Take a look at this fiddle in IE: http://jsfiddle.net/ygCcc/1/ You'll notice that the first block indicates around 157 properties, whereas the second has 255. These extra ones are courtesy of MooTools, and help make everything work nicely. (In other browsers, you'll see that these counts are nearly identical -- the only difference is the addition of a UID when accessing the element with MooTools' methods.)
This is why when you use document.id to "help out" the code, things will start working correctly in IE. Without it, those elements aren't moo-ified.
Hope this helps! -- Barry van Oudtshoorn www.barryvan.com.au Not sent from my Apple πPhone.
