Now let me introduce you to a main feature of this tutorial - the "Test Box" AKA "T-Box".
aler("This is wrong")
Nothing is shown(by default). This is because there was an error('alert' is spelled 'aler') and your browser suppressed the error message. You should turn on the error notification of your browser if you wish see the errors you have made - trust me, they will be many. Just do the following for your browser.
Microsoft Internet Explorer
Choose Tools -> Internet Options, and select the 'Advanced' tab. Make sure that the 'Display a notification about every script error' is ticked. Click 'OK' to save the setting.
See browser documentation to see how this can be done.
If done correctly, the above example(
aler("This is wrong")) will show an error 'Object expected'(IE) or 'aler is not defined'(Mozilla).