how to remove flickering when the data is being postback

Hi,
I am using an update panel in my application which has two dropdownlist boxes in it. The items list for each dropdownlist box is dependent on one another. When I select the item of one dropdrownlist box, the contents of other dropdownlist box is also getting changed. But the page becomes blank for some time and after sometime the contents appear in correct stage. The problem for me is that even though I am using ajax update panel the time taken to refresh is more and flickering occurs. How to remove this flickering from the page? Please provide me help ASAP.

Thanks in advance.

I had a similar problem with flickering once. Since you can't control what the browser is doing while you're updating the DOM, what I did is hid the control first, updated it and then made it visible again. You can even have a hidden overlapped image or duplicate control as a sort of "visual placeholder" if you'd like. When you hide the control for updating, show the placeholder and vice versa.

This works well when updating lists or select boxes with large data sets.

Not a direct answer, but for large chunks of text, I generally put a transparent div over them, use that for a fade out affect by making it opaque. This also gives time for complex ajax scripts to run. Then, once it's returned, replace the data, I fade the div back out (and remember to set it to block=none to avoid strange mouse effects).