How to get screen size with Javasript

Get screen width and height by using Javascript:

var screenW = 800, screenH = 600;
if (parseInt(navigator.appVersion)>3) {
screenW = screen.width;
screenH = screen.height;
}
else if (navigator.appName == "Netscape" && parseInt(navigator.appVersion)== 3 && navigator.javaEnabled())
{
var jToolkit = java.awt.Toolkit.getDefaultToolkit();
var jScreenSize = jToolkit.getScreenSize();
screenW = jScreenSize.width;
screenH = jScreenSize.height;
}