Show / Hide DIV According To Link URL

I am pretty new to JS but I've managed to create a function to show and hide a div according to a link's URL, but I am gonna have lots of url's and lots of div's to show and hide, its not a problem to show and hide them, the only trouble is that they stack, if I show div 1, and then press link 2 to show div 2, Div 2 is gonna be below div 1, and what I want is that when I click link 2 to hide div 1 or any other shown divs, I am sure its possible but i don't know how to do it. I think it would be possible by storing the id of the div in a variable, but the only problem is that when I call that function, the variable always changes so it would be a matter of storing the id in a variable outside the function, but i don't know how to do that, or what are the rules?

This is my code:
JS
function showHide(product) {
var el = document.getElementById(product);
el.className = (el.className == 'hide') ? '' : 'hide';
}

HTML
<div id="1" class="hide">Content of Div 1</div>
<div id="2" class="hide">Content of Div 2</div>
<a href="javascript:showHide('1');">Show Hide 1</a>
<a href="javascript:showHide('2');">Show Hide 1</a>

CSS
.hide {
display:none;
}

I need to have the javascript function call in href because of an applet I am using. In resume, the divs are hidden at the start, when I click one link, the div shows, when I click the other link I need the previous div shown to be hidden (class="hide"), and show the new div and so on.