Opening window after clicking on popupwindow's link causing the window to pop up behind the first popedup window on Internet explorer

I am opening a popup window from WebForm using JavaScript "window.open()" after window is opened a link button is used for the same for 'open a popup window' but the link on first popup window causing the next popup window open behind the first popup window in internet explorer, in chrome and Mozilla its working showing the last popup window on top.