Update
Sorry, I should have looked at your source first. Here is how you need to change your code. The important thing to realize, is you can't get the width until the image has fully loaded. That is why I use a load
event callback to retrieve the widths:
// Create the img element, add a load handler, then append it to the body
var $img = $('<img class="zoomIcon" alt="zoom icon" />').load(function(e){
// get icon image properties for use with animation
var imageWidth = $(this).width();
var imageHeight = $(this).height();
// ... any code that uses these variables needs to go in here ...
}).attr('src', zoomImage).appendTo( document.body );
Original Answer: This is general information.
You are probably putting this code in document.ready
which will try to retrieve the width before the image has loaded. Try this instead:
$(window).load(function(){
var imageWidth = $(".zoomer").width();
alert( imageWidth ); // Should be correct
});