http://demos.telerik.com/aspnet-ajax/tooltip/examples/hideevent/defaultcs.aspx
"Hide on event :Default - hides when mouse is out of the target element" is not working as expected
if you leave the mouse pointer on top of the target and don't move your mouse at all, the tooltip will close after few seconds. Expected behavior would be that the tooltip stays visible until you actually move mouse out of the target element. I tested this with IE, Chrome and Firefox with similar results.