use the attached monitor.zul and the config in zk.xml

<listener>
<listener-class>org.zkoss.zk.ui.util.Statistic</listener-class>
</listener>

open the monitor.zul in chrome browser and another browser e.g. FF

refresh the URL should not lead to increasing number of active desktops
(the number should not exceed 2 per browser, since the rmDesktop command after refresh is sometimes processed later)

in chrome the number of active desktops will increase with any refresh (back/next, or ENTER in URL) until the max desktops in session limit is reached (15 by default)...
while the number will remain constant in FF or IE

when closing a tab in Chrome the rmDesktop command fires correctly

it will then take a long time to clean up at the server side depending on the desktop timeout config to reduce the number of desktops and may lead to memory issues on that server

Current workaround is to keep the max-desktops-per-session param as low as possible
http://books.zkoss.org/wiki/ZK_Configuration_Reference/zk.xml/The_session-config_Element/The_max-desktops-per-session_Element