We define a listbar header image for the collapsed, hover and expanded appearances.  We set the image by using something similar to <style BackgroundImage="..." .

Our problem is that this image continually gets requested.  Every time a user moves the mouse over the listbar (hover) the image is requested.  It is requested via an HTTP 304 request.  Shouldn't this image be cached? 

Here are some other notes about this issue:

• This didn't seem to happen in the 7.3 version.  We upgraded to 8.2 and are seeing it for the first time.
• We see similar issues with UltraWebGrid header images
• We noticed a similar flavor of this issue in 7.3 where the WebResource.axd was fired a lot.  Removing the following in the web.config helped that issue, but not this new issue <compilation debug="true" ...
• This is a huge traffic consumer, so we'd appreciate any guidance ASAP.

Thanks!