<script language="javascript" type="text/javascript">

    $('#navAboutImg').click(function(){
        $('#contentFavorites').slideDown("slow");
        $('#contentContact').slideDown("slow");
    });
    
    $('#navFavoritesImg').click(function(){
        $('#contentContact').slideUp("slow", function() {$('#contentFavorites').slideDown("slow");});
    });
    $('#navResumeImg').click(function(){
        $('#contentFavorites').slideUp("slow");
        $('#contentContact').slideUp("slow");
    });
    $('#navContactImg').click(function(){
        $('#contentFavorites').slideUp("slow", function() {$('#contentContact').slideDown("slow");});
        return false;
    });
</script>

Nothing is happening. when I click Those images!

Might just be because you are missing a document.ready:

$(document).ready(function() {

//put all your code in between here

});

Next time post all your code including the html.