Need some help in coding chrome extension.

Hello guys, actually i am learning to build chrome extension. I need a extension which accepts user login and after authenticate user it print "Hello".
Can anyone help me in coding this simple application ?

If it has to "authenticate", then it have to make a callback to a script hosted somewhere and verify if the credentials are valid. Its not a simply application like you think but its not tough either to code it yourself if you know java, html and css.