Ghosting inappropriate buttons
In this example, the current page is, quite logically, removed from the range of choices of pages that you can go to by 'ghosting' the link button. This mechanism requires that the destination page is clearly titled elsewhere using static text.
Another way is to make the HOME button become the actual place name instead of a pointer to it. That is a fairly subtle distinction but many interface design mechanisms are subtle. In real life, you can fence-off an area of ground to keep people from straying onto it or you can simply pave the area with sharp stones. This is using 'visual communication' instead of brute-force, physical barriers.
Many navigational systems use another real-world metaphor, the radio button. The mechanical buttons on old car radios were used to tune into preset stations. One was always pressed in, the others remained out. When you press another button, it goes in and the previously selected one pops out. This was known as a 'latching' buttons and provided good visual feedback in the absence of LCD displays.