It could be the response callback. But I have spent a half a day optimising the callback code for speed. I have seen some dramatic improvement - response delays of 3-4 seconds dropping to 1-2, but it still feels sluggish.
There are two main ajax calls. The first is only called once when the page is loaded. It responds with a large data set that is then used the build the page. This call can be quite slow, but as it only happens once I can live with it. The second AJAX call is made when the user clicks on an element built in step 1. This call collects data from the interface on the clicked element(s) and submits it, then based on the returned data it updates the state of the displayed elements. While this update does not alter the structure of the page (no DOM elements are created or destroyed), it does add and remove classes from elements and then based on the classes, animates the show/hide of elements. This is the section I have optimised. >From what I have seen there are two factors slowing down the response. The first is the actual AJAX response in IE7. The second is the post response processing. I am looking for suggestions on fixing the AJAX response time in IE7. The other I can address already. I will see about getting a link to the running code. It is for a client site that has not gone live yet. It is a large and complex application though, so it might be overkill.
