I think the for (var i in ...) is the problem. My guess is i is not an integer, but an object (element).

I think you should store the document.getElementsByClassName('someclass') in an array and...

1. The reason I use div's is because span's often give me trouble.
2. toggleClass toggles a specific class on and off, so you can't use it like you do now
3. I gave my div the id #toggle, so I...

Damn... missed it completely. Your <label> tag isn't correctly closed. It is closed with </font>. Replaced it with </label> and now it works in Opera and IETester.