I'm updating a form in my West Wind Web Store that provides resorting of items dynamically in the browser without reposting the entire form. I've been running the form both with IE and FireFox and noticed that IE was 'flashing an awful lot' while doing the AJAX style callbacks to the page.

The form basically ships back the list data and then sends it back resorted. It's not terribly efficient as it ships back the list content (as a JSON object) but it's still drastically faster than reposting the entire form.

Here's the form:

http://www.west-wind.com/webstoresandbox/admin/SpecialsManager.aspx

As it turns out the problem I ran into here were the IE browser cache settings. At some point during debugging I had turned on the 'Always Refresh Pages' option in the IE cache settings. And IE apparently overeagerly applied it itself not using local caches for any linked files like images and CSS files.

You can try that out yourself – switch the browser cache mode and run the form again and notice how much of a difference that makes on the visual appearance of the form execution. You'll see the image buttons and logos repaint themselves for every sort/move/delete operation resulting in a POSTBack style feel even though the sorting is done using Callbacks (this is using wwHoverPanel's JSON remote page method calls).

I've noticed this in other applications as well – especially in things like hover panels, where all images used in the popup windows redraw, seriously diminishing the whole 'clean' popup effect.

So moral of the story – for optimal AJAX style display you'll want to try and make sure that normal cache settings are in place or the idea of a 'no-flash'.