Opens a popup for the specified url, if null simply open a popup for the current site.

Site.js

javascript:(
	function() {
		var doit = prompt("Enter a sitename");
		var args = "https://" + doit;
		var params = "width=1100,height=550,left=75,top=20,resizable=yes,scrollbars=yes";
		if (doit != null) {
			if (doit.indexOf('http') >= 0) args = doit;
                        window.open(args, "_blank", params);
		} else {
			window.open(window.location.href, "_blank", params);
		}
	}
)();