var WindowObjectReference = null; // global variable

function openPopup(href) {
	if(WindowObjectReference == null || WindowObjectReference.closed) {
	/* if the pointer to the window object in memory does not exist
	   or if such pointer exists but the window was closed */

	args = "height=800,width=600,resizable=yes,scrollbars=yes,status=yes";
	if (arguments.length == 2) {
		args = arguments[1];
	}

	WindowObjectReference = window.open(href, "", args);
	/* then create it. The new window will be created and
	   will be brought on top of any other window. */
	} else {
	WindowObjectReference.focus();
	/* else the window reference must exist and the window
	   is not closed; therefore, we can bring it back on top of any other
	   window with the focus() method. There would be no need to re-create
	   the window or to reload the referenced resource. */
	}
}