Purpose of grid.png?

I'm just wondering about the purpose of grid.png. I am doing some development on a machine that runs a pretty complex authentication scheme against requested files. Accidentally, I had grid.png also authenticated and it took a noticeable amount of time for the browser to download this image. Until it was downloaded, I found I could not use the onclick event. In a production environment, this file will not be authenticated, but this situation led me to wonder what if the user had a slow connection? They would not be able to click on any rows until grid.png was downloaded.

So what is the purpose of this file?

Grid.png only contains sort indicator images and column separator image (for xp skin). I don't think it should affect onclick event. Are you absolutely sure it is the case?

Whe I did the trace :
http://www.activewidgets.com/messages/2250-1.htm
"don't remember well", but seems to me that was "onmouseover" event
(in xp style fires a higlight)..... could it be?
Thanks

Not sure why this is happening but I am absolutely certain it occurs. However, it may be this was a unique instance and is not really something to worry about. I actually discovered the problem on my end - the grid.png file was in the wrong location and the test server I was using was not responding back to the client that the file could not be found so the browser kept waiting for a response on the file. This seemed to prevent the onclick even from firing.

However, I doubt this is an event to really pay much attention to. In a production environment, the web server would most certainly return a response of 404 on the missing file almost immediately. And if the server had the file, it would begin streaming back to the browser instantly.

Sorry for raising a false alarm.

Alex