Am I wrong to say you should never use onclick in an element as this would be contrary to the purpose of using jQuery which means onclick would totally bind mark-up to javascript? So it would not be unobtrusive in that case.
And can't you do this another way other than this: document.getElementById("productImage"); And what about this, isn't the point of jQuery is to use Load? $(document).ready(function() { prodImage = document.getElementById("productImage"); prodImage.onload = extraLargeLoad; });