Ok remove previous code from footer.php and css from your custom.css and add this to you footer.php now. And copy facebook-logo.png to your root directory of osclass installation.
<style type="text/css">
/* facebook box */
.tufflikebox{background:url("facebook-logo.png") no-repeat scroll left center transparent!important;
display:block;float:right;height:320px;padding:0 5px 0 46px;width:245px;
z-index:99999;position:fixed;right:-250px;top:20%}
.tufflikebox #tuffid{background-color:#fff; border:none;position:relative;display:block;}
.tufflikebox span{bottom:12px;font:8px "lucida grande",tahoma,verdana,arial,sans-serif;
position:absolute;right:6px;text-align:right;z-index:99999}
.tufflikebox span a{color:#808080;text-decoration:none}
.tufflikebox span a:hover{text-decoration:underline}
</style>
<script type="text/javascript">
//<!--
$(document).ready(function() {$(".tufflikebox").hover(function()
{$(this).stop().animate({right: "0"}, "medium");}, function()
{$(this).stop().animate({right: "-250"}, "medium");}, 500);}
);
//-->
</script>
<div class="tufflikebox" style=""><div id="tuffid"></div>
</div>
<script type="text/javascript">
//doesn't block the load event
function createIframe(){
var i = document.createElement("iframe");
i.src = "http://www.facebook.com/plugins/likebox.php?href=http%3A%2F%2Ffacebook.com%2Ftuffclassified&width=245&colorscheme=light&show_faces=true&connections=9&stream=false&header=false&height=320";
i.scrolling = "no";
i.frameborder = "0";
i.width = "245px";
i.height = "320px";
i.style = "border:none; overflow:hidden; width:245px; height:320px; background:#fff;"
document.getElementById("tuffid").appendChild(i);
};
// Check for browser support of event handling capability
if (window.addEventListener)
window.addEventListener("load", createIframe, false);
else if (window.attachEvent)
window.attachEvent("onload", createIframe);
else window.onload = createIframe;
</script>