[thelist] JS add remove list items

[fstorr]

Hi all

I'm trying to replicate a very basic powerpoint type functionality in 
JavaScript.  The idea is to have subject headings as bullet points that 
will appear when a "next" button is pressed. The page will start with no 
bullets showing. When a "previous" button is pressed, the last bullet 
item is removed.

My JavaScript isn't by any means great, and I've got this far, but can't 
work out the rest.  At the moment it just takes off/adds back the top 
one.  I've also noticed an annoying bug in Moz1.5 where the bullet point 
isn;t replaced when the fist bullet point is put back in. Any help would 
be appreciated:

<ul>
<li>one</li>
<li>two</li>
<li>three</li>
<li>four</li>
</ul>
<p onclick="return bullet('add');">change +</p>
<p onclick="return bullet('remove');">change -</p>

function bullet(action)

{
var counter = document.getElementsByTagName("li");
for (i=0; i < counter.length; i++)
{
  if (action == "add")
   {
     counter[i].style.display="block";
     alert(counter[i].value);
     return;
   }
else
   {
     counter[i].style.display="none";
     alert(counter[i].value);
     return;
   }
}

}