1 button does not work(simple navigation)

[font=Arial]I have to be kind of slow thinking dude if in that simple file what I got I can not figure out why the button #4 does not work.[/font]

[font=Arial](I admit I created only the last one b/c menu of 3 is not enough). Does someone know how to involve that issue before I will go crazy? [/font]

[font=Arial]I would be thankful.[/font]