Javascript function to open a popup

This is a very important and handy javascript to open a popup window, useful in showing small bits of information to user without taking them to different page.

<script> function popup(url) { newwindow=window.open(url,'popup_name','height=500,width=400,left=100,top=100 resizable=yes,scrollbars=yes,toolbar=yes,status=yes'); if(window.focus){newwindow.focus();} } </script>

This function can be called on any event like mouse click by passing the url of the page to be opened in a popup.
Please Note: Firefox does not allow the popup window to be non resizable, hence this feature can not be seen in Mozilla Firefox.